Very neat idea, however, if you have access to a welder, it's probably pretty easy to make something. I may give that a try and report back.
Can't beat a strong back and play testing. My wife's always telling me that I need more exercise.
I think pinball skates would also work well.
They essentially do the same thing as the single leg lift but you can adjust two legs at a time. Their also great for moving machines.
Edit: Actually, they come in pairs so you could adjust all four legs at the same time.
I have skates and I can't imagine trying to level the game with those on there. They pop off all the time and are not a perfect fit for many games. They are good for moving games, but not for leveling.