Try www.briggsbits - they seem to stock all kinds of parts for Briggs & Stratton engines.
For other lawnmower spares try "OldLawnmowers" - think thats right. I used them to find parts for a 1963 Colt cylinder mower and found them very useful. Apologies, I can't find the correct website name.
Mike Giles
April 2015
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.