Help! Where to buy infant boys dress shoes?

My 15 month old son is in his aunt's wedding next week.  I've been looking everywhere for dress shoes for him with no luck.  He wears a size 5, but he's got very wide feet.  Most shoes won't fit over his fat feet.  If I try a size larger, they fit the width but are too roomy in the heel/toes.

I've tried Payless (which has some great velcro dress shoes, just not in a 5), Walmart (which don't come in wide, and thus, don't fit), Target, and Burlington Coat Factory (those wouldn't fit on his feet, either). 

Tomorrow I'm going to try a 3rd or 4th Payless, Sears, and maybe consignment shops.   I don't know where else to go.  I don't want to spend a ton of money on shoes he's only going to wear once.  I'm afraid to order anything online since I won't know if it'll actually fit, or whether it'll even get here in time.  Does anyone have any ideas? 

I live in the Chicago area and around here we have stores dedicated to events like First Communions, Quincenetas (latin version of sweet 16's), Confirmations and stuff like that.  Those stores carry little boys tuxes, dress shoes, everything of that sort.

Have you tried a regular tuxedo store for a suggestion?

these are a bit pricey but according to moms everywhere, stride right is worth it....

you might be able to find them on ebay.

here is one from ebay.  size 5, black, target brand.

these are stride rite.

here are some that are 5W

Marshalls, Filene's Basement, TJ Maxx.

Thanks for all the suggestions!  I'm going to go out today and continue the search! :)