You'll have trouble finding a clip for a Browining BLR 81 since it uses a box magazine. That aside, you will apparently have trouble finding a magazine in .223 as well, since that appears to be a rare caliber. You can find magazines in almost any caliber but the .222/.223
Midwest Gun Works might be the source for you though: They don't offer a full replacement magazine BUT, they do offer the parts to build one up (if in stock):
http://www.midwestgunworks.com/page/mgwi/ctgy/BLRP812Contact us - Phone: (636)475-7300
Fax: (636)475-7303
Email: customerservice@midwestgunworks.com
Good Luck
Charon