Here's an option... find out what exactly they need to know about the "installing" profession and their "company". Just a name and a bill on official looking letterhead? Will they actually need a TIN for them or anything?
In many states, setting up a "company" is actually quite easy, esp if you don't actually charge or make any $$.
Just file for a business license and make up a business, "Cool Toyota Guy" or whatever..
Now make up some letterheasd, and a bill that statest he work, and billed not for cash but "traded for in-kind service".
It always comes back to teh definition of "professional"....