Dear Battletech Players: Please Help

Okay, so my son likes Battletech.  Which is cool, seeing as I used to play myself.

Except... where to get him started?  He's fifteen, and from what I've seen of the Quick Start PDF, that's right about his level.  But the Introductory Box Set that keeps getting referenced (even on appears to have been out of stock since forever.

So what's a good starter pack of minis to go with the PDFs of the rules for me to gift him?