We have redesigned from scratch a key cap for my Atari 1040 STF with @BF 

We made it in 2 parts so it will be easy to print and fit both pieces together.

Not tested yet, but very promising looking right now.

Of course, color will always be an issue... But hey, better with a key than nothing.

I took the opportunity to print also some floppy holders to help clean these old disks:

5"1/4 , 3.5", 3" (yes also for Amstrad/Sinclair spectrum)