It may be tough to find wheels with the keyed hub that you are looking for. You may have to buy a wheel and design your own hub to press into it.
Some good places to look for wheels:
www.mcmaster.com
www.robotmarketplace.com
Team 121 is using 2" x 4" colson performa wheels (from robotmarketplace). They were around $7 each. We made our own keyed hubs out of aluminum and pressed them in.
Good luck in your search.
Rob