You can 3D print a wheel, smooth it out (very important or it will be hard to get the wheels out of the mold after pouring), make a silicon mold (2 pieces) and pour wheels from urathene. But the urathene we use in wheels are very different most thane. It’s high rebound, 78a duro at its best. But it need to have a high tear resistance. In pouring wheels with hummie, none held up in the long run. Had a&e pour us proper wheels and these have lasted properly so far.
You can make your own wheels, but finding good thane is the hardest part. Beyond that, expect to waste at least 50% of the thane you buy from bad pours.