once upon a time back in the days when garages were even smaller and shorter (think model T) the early travel trailers used to come with a set of steel wheels that did not have tires
on them. They were made to be switched out so you could store the trailer in a garage.
You could have them custom made at a fabrication shop. You only need two of them. Of course you would want to adhere some rubber strips around the edges to protect the garage floor. Just be sure the plate(s) are thick enough to bear the load that is being put onto them.