Do you really move your tank often enough to make this necessary? Personally I try not to move my tanks much, let alone the bigger ones once they are set up. Draining and filling and transferring livestock? No thanks.
If you do find this absolutely necessary, they got some pretty decently cheap heavy duty casters at mcmaster.com, actually they have everything there. I could probably come up with a way to do this but it wouldnt be easy because any mounting part would have to be recessed and structurally sound otherwise your mounts are going to dent your floor good when you fill the tank.