The moniker "British Bulldog" was evidently not internationally tradmarked as Forehand & Wadworth, Johnson, Bye & Company (precurser to Iver Johnson Arms & Cycle Works) and probably several different small gunmakers in Liege, Belgium marketed revolvers under this model name; likely yours is one of the latter. The only Clement gunmaker that I can find information on is the inventor and manufacturer of autopistols in Liege in the years immediately prior to WWI. There is no indication that there is any relationship between this Clement and the Liege manufacturers of "British Bulldog" revolvers as Liege was one of the major gunmaking centers in Europe at the time and had many manufacturers, mostly small and producing guns of mediocre quality, many of them not marked as to the manufacturer.
You have a very obscure item and spare parts are probably about as common as toothbrushes for chickens, but try
:Numrich/Gun Parts Corp. doesn't list all the parts they have in stock on their website; you might contact them for what you need at help@gunpartscorp.com.
If you still don't have any luck with them try:
Websites that may also have gun parts:
www.auctionarms.com
www.gunbroker.com
www.ArmsBid.com
www.gunsamerica.com
www.armchairgunshow.com
www.gunlistonline.com
www.gunpurchase.com
www.gunshowonthenet.com
www.gunsinternational.com
www.SpokaneGunAuction.com
eBay (go to GUNSURPLUSPARTS, I think)
You might also find a broken or inoperable "parts gun" for sale on one of these websites, which can be cannibalized for the parts you need. You can sell the remaining parts on the internet, or this forum's host. Re-post here if you aren't familiar with purchasing guns across state lines.
www.brownells.com (parts for certain late-production firearms only)
www.poppertsgunparts.com
Bob's Gun Shop at www.gun-parts.com, or www.gunparts@hsnp.com and (501) 767-1970
Brock's Gunsmithing Inc. www.brocksgunsmithinginc.com Click on "parts"
www.colt380.com
Out Back Gun Parts (812) 945-0480
www.jackfirstgun.com (605) 343-9544
www.gunpartscorp.com
Rusted&Busted Bob's Box 24 Whitmore Ca. 96096
www.yourgunparts.com
Western Gun Parts, www.westerngunparts.com/default.htm, 1-403-489-5711 (Canada)
Jim Wisner (206/360) 748-8942 360-748-4590 www.wisnerinc.com (obsolete firearms parts)
Jim Horvath, P.O. Box 791548, New Orleans, La 70179-1548
www.sarcoinc.com
Ken's Parts and Guns in Irving, TX
lnh555@sbcglobal.net and randyman@ncidata.com (Broomhandle Mauser parts)
www.1896mauser.com/index.html (Broomhandle Mauser parts)
http://www.buymilsurp.com and http://www.surplusbunker.com (parts for various imported and military surplus guns)
Glend Arms Mfg. Co., PO Box 361, Secane, Pa. 19018 (manufacturer of firing pins)
Marstar Canada www.marstar.ca (British Commonwealth military arms)
www.coltparts.com (original and some reproduction parts)
www.ssporters.com (parts for old handguns, curios and relics)
Liberty Antique Gunworks, 19 Key St., Eastport, Me. 04631 (207) 853-4116
(obsolete S&W parts)
High Standard parts (203) 239-1012
www.savvysurvivor.com/handguns_and_handgun_magazines_f.htm
Hoosier Gun Parts, www.hoosiergunworks.com
Marty's Gunsmithing, 371 Spring Valley Rd. Elko, NV. 89801 Ph. (207)738-2666 (obsolete Remington parts)
www.oldwestgunsmith.com, dave@oldwestgunsmith.com (old handguns, esp. Smith & Wesson parts)
www.vintagesporting.com
www.robertrtg.com
www.leesgunparts.com
www.ellwoodepps.com
Tom Heller, Heller Arms, Ltd., P O Box 398, St Charles MO 63302 Phone: (636) 447-3006 E-mail: hellerarms@webtv.net
www.Bryco-Jennings-JimenezArms.com
G.S. Armatt,Inc. 335 Gay Road, Zebulon, NC 27597, (919) 269-8449, armatt@aol.com
Earls Repair Service, Inc. , 437 R Chandler St. Tewksbury, Ma., 01876
978-851-2656. http://carlwalther.com (Walther parts and service)
http://www.topgunsupply.com/gun-parts/ (Glock, GSG-5, HK, Kahr, Sig Sauer, Wilson, AR15)
www.bersafirearmsusa.com (Parts for Bersa, Firestorm (Llama) and Comanche (Llama) handguns)
Unique/M.A.P.E 10 Les Allees F-64700 Hendaye FRANCE (Parts for French-made guns)
www.tanfoglioparts.com (Parts for Tanfoglio-made autos, possibly including EAA Witnesses)
www.vtigunparts.com, mail@vtigunparts.com, VTI Gun Parts, PO Bx 509,Lakeville, Ct. 06039 (Parts for Uberti, Peitta, Pedersoli, Ruger, Colt and USFA replica and reproduction guns.)
John D. Bush. johnd.bush@yahoo.com and/or amsales@mindspring.com (Magazines and parts for FEG pocket autos and Tokarevs)
Miga Gun Parts, a division of Midway Guns, PO Box 569, 9754 E Oglethorpe
Hwy, Midway, GA 31320, Phone: 912-884-5616 or 884-5597, e-mail:
midwayguns@coastalnow.net, www.galleryofguns.com, Ask for Penny
Dixie Gun Works in Union City Tenn (Colt and replica handgun parts)
John A. Kopec (916)472-3438 (Colt grips)
Egyption Helwan parts: M&M Gunsmithing (703)739-2150
Old West Parts Bin, 1463 Funston Ave., San Francisco,Ca. 94122 (antique guns)
Stevens Sight & Tool Co., RD 1 Box 307C, Effort, Pa. 18330 (215)681-5670 (Old Stevens firearms)
Ed Cox..Circle C X Antiques. PO Bx 2197, Fernley Nv. 89408 (775)575-6205 (old handguns)
Springfield Sporters, (724) 254-2626, Mon-Fri 0900 to 1700 hrs EST/EDT
http://www.germanguns.de/exportindex.htm (German and maybe some other European firearms.)
PHH,Inc., 1330 Center Ave.,Pittsburgh,Pa. 15229 Ph#412-766-6100 (Ruger parts)
WAFFEN WIESER GESELLSCHAFT M.B.H. at http://web2.cylex.de/firma-home/waffen-wieser-gesellschaft-m-b-h--4384190.html or http://www.steyrwaffen.at or www.cds.ehrenreich.de (Parts for Steyr, and perhaps other old Austrian or German handguns)
www.fultonsofbisley.com or Terry Abram +44 (0) 1245 231753 (United Kingdom) (British Commonwealth guns)
www.thedealershowroom.com (military rifles and pistols)
For more listings go to http://www.brownells.com/categories.aspx?c=4815
Some vendors have a "wish-list" on their web pages....check their site for such a feature and add you wants to it.
Also, try to post on some want ads boards, (gunbroker.com has one as does auctionarms.com) or ask questions at some shooters forums. Search for some here: www.gunshow.net/links.htm
There's other possibilities if you don't have any luck with the above. Re-post here.