just take the cat to a scrap yard.
rock auto appears to have stock replacement walkers, plus there are rebates and our discount code in the sponsor section. not sure you'll beat that for stock replacement bolt on.
http://www.rockauto.com/catalog/raframecatalog.php
WALKER Part # 53438 LH $194.79
WALKER Part # 50540 RH $334.89
$30 rebate:
http://www.rockauto.com/lang/en/promo.html#walker
RockAuto Discount Code - Valid through 6/3/2011
5% Discount Code: C204C5E76BF5
Damn, RH is a lot pricier. Your other option is go to a muffler shop and have them weld in a universal fit.
Be ready, when one goes the other is not far behind. you might consider doing both.
Walker catalog shows WALKER Part # 93238 is the universal fit you'd need welded in. (rockauto $99.79) so that is your guide, maybe $125-150 a side installed at the local exhaust place.