Steel wheels will be hard to come by. Most people want to go to rubber so the tractor can be seen in parades. Steel wheels means you must keep it on the trailer for a parade.
Otherwise lots of places that sell parts.
Steiner Tractor Parts
http://steinertractor.com/
Tractor Parts ASAP
http://tractorpartsasap.com/ They also have a tractor junkyard and may be able to find you the steel wheels.
Amazon has vendors that sells parts.
If you have a Facebook account search for Farmall Group.
Another way I found vendors for tractors that I work on is to search Ebay. Alot of vendors will sell their parts there and you might be able to haggle the price.
Good luck and dont forget to post pictures. We love to see what other people have.