I used 10mm standoffs and 6mm laptop screws (both M2) on a 1.5mm stainless steel plate (Poker II case).
I did have to cut off part of the male end on the standoffs as they were too long to fit in the holes in the case, but that was a quick and painless task.
Also, I did not like the angle of the Poker II case, so in addition I filed down some of the standoffs to allow a steeper angle, but that was just for preference.
Keep in mind that you'd have to make sure that the holes on the plate need to be smaller than that of a normal plate, as you'd mount your screws on it instead of on the PCB.
Anyways, you could find both the screws and standoffs on sites like Amazon, that's where I got mine at least.