Is it possible to create your own wheel?
You can always brick-build a wheel.  The curved slope pieces can closely approximate a circle.

For example, 12 4x1 curved slopes gives a circle with a radius of 160 LDUs (8 studs).

For more information on brick-built wheels, I suggest you refer to the "Brick Built LEGO Wheels Book": 



http://www.ultimate-design.org/2014/05/unofficial-free-brick-built-lego-wheels.html