[IKE]

Originally Posted by 548swimmer

http://www.harborfreight.com/6-inch-...eel-97183.html

Try these, they're a touch wide but they are 6 inches.

I think that one has a 6" rim, and a 12" diameter tire.

McMaster has a pneumatic caster tire:
2717T51
Pneumatic Wheel for Casters Gray, 6" X 2", 3/4" Axle, Ball Bearing, 200# Cap
In stock at $19.27 Each

It has a split rim that would require some sort of adapter or custom split rim (as mentioned above).