My previous response was a little terse.
You can use part #222-108 diesel traction tire.
It fits postwar and MPC diesels
The train tender sells them individually and in bulk.
They are 24 cents each by the dozen, 20 cents each by the hundred, and 40 cents each by the piece.
Since they are a commonly needed item, I buy them by the dozen.
I store mine in a ziplock parts bag, in a drawer. I have yet to have any dry out or go bad.
http://www.ttender.com/index.htm