Two suggestions:
ONe search the shop talk forum. Lots of cheap forge plans there, from Wayne Goddards's one brick forge(one soft fire brick, some wire, and a propane torch) to several variations on the weed burner forge, which consists of a 19.99 harbor freight weed burner and a pile of fire bricks, up to a full 6 bunrer sword size one, and everything in between.
Other option is jsut to buy Wayne Goddard's $50 knife shop. Several ideas in there, coal, charcoal or gas.