Well it's official!

My tire changer has a built in air tank.
It's used to blast seat the bead, but also to air them up.
Mine is made into the vertical part that holds the "duck" arm, and has a seal leaking deep within, so not real feasible to repair.
It works great as long as the compressor is on.
That's one of the reasons it was cheap.

I do see more modern changers and balancers on CL frequently.
Usually in the $700-$1500 range each.