G'day, I've got a problem

I bought a three wheel band saw at a deceased estate sale, It has no identifing mark/ tags /name. but I think it maybe a CRAFTMASTER,
the problem is the tire on the bottom wheel has gone hard and peices had come away from it(big bits) have tried to cut a bicycle tyre and stick it on , it works but no matter how i adjust it , the teeth run on the alloy, does anybody know where i can buy a 6inch tire? i'm running a 6mm wide blade at 6 tpi; with a length of 1785mm
I found large ones at sydney tool but they don't have 6',,,, CD.