I thought it would be like a IF stim or something.
those products look to be mostly fancy massage "'helpers"

I don't think he would need that exact machine being used by a PT - it sounds like it is more to help the PT person not get overworked or strained.

Does he have ins coverage for a good PT /massage?

There are a couple types of electric stim machines - the IF stim can be set to do almost the same thing just by using small amounts of electricity to the muscles.

The muscles do the work and the PT or DC just places the pads on the pt and monitors the settings. making adjustment to them if needed.

Many PT places use the IF stim machines - you might ask about those and he could try it to see if it does a similar benefit for him.