Find a Couple's Registry & Wedding Website
Attire and Accessories
Invites and Paper
Not Engaged Yet
Engaged & Proposals
I got my ringbearer a tux on Amazon for $35 check there.
Depending on your colors you could also try Kohls. We have bought Easter outfits there a few years for my soon to be SS. They always seem to be running a sale. Plus if they don't have what you want in stock you should be able to order from the store kiosk at the sale price.