Wheel Help!!

I was wondering if anyone could help out my team. We are trying to find wheels that are 11 to 12 inches in diameter and no bigger than 3 inches in thickness, that are plastic, and treaded like the wheels that are in the kit of parts

Can anyone recomend a good site that I could buy these kind of wheels from. Currently i am struggling a lot to find some place were i can buy this type of wheel.

any help is greatly apreciated!

All sort of large thinner wheels at: