I wish your friend all the best in his search, but I wouldn't hold my breath. The B3 is such a high dollar item, it's likely outside the realm of possibility that you'd find an empty B3 cabinet. Either they're being used or it's been burned to the ground. I don't think anyone in their right mind would let a B3 cabinet sit empty.
Your friend could have one made, but that would probably be equally expensive as a fully loaded B3.
Prime example of the B3's value. A gentlemen just recently told me he owns several B3's. One particular B3 is a 1969 Cherry finish, immaculate condition. He said he would never sell it, but if he did, he'd want no less than 10.5 grand for it.
Guess I better start buyin' me some lottery tickets, LOL!
No I'm kiddin' with ya...
Take care,
Ryan