[Oni]

You're probably better off buying a new laptop (or possibly desktop, if you enjoy upgrading). If you're only switching between a 920M to a 940M, it's probably not worth the effort. Gpuboss says there's a 0.3 difference between those cards (on 1 to 10 scale).

causing Nvidia to have to RMA it and I doubt OP could figure out how to replace it by just wingin' it

Pretty much what I implied. They're likely unavailable, because the average consumer is not capable.