GEMRM

You should ALWAYS anchor your machine down with a seat belt. In the event of an accident, a machine that is wedged between the back/front seats on the floor or any where else becomes a heavy projectile. You never know what another driver might do and safety for the occupants of the car is important.
I have a travel bag and a hand truck . I belt the travel bag to the hand truck to move from house/store to car. Then I unbelt the machine bag, put it in the back seat, secure it with a seat belt and then fold the hand truck up and secure it with a cord.
I couldn't afford to replace a machine that fell over and in an accident, I don't have to worry it's going to become a lethal weapon.
If you can find a rolling suitcase of the right size, it would work , just anchor it.