The old T410s and T420's have the nicest optical drive bay system I've come across. I understand the desire to make thinner lighter laptops, and the T420's are built like tanks (so much so that I've bought one off eBay that had probably been dropped down the stairs -- lid was beyond repair, so I just make a slabtop out of it and it works fine in a dock as a quiet power-efficient desktop, or as a network server.
Anyway, I'll put the answer here if and when I find it, but I wonder what the correct search term is for these bits:
