This was created as a birthday present for a friend.  I took a model of a standard MX Keycap (row 1) and added an extrusion of an SVG of the Atari logo.

Prints best a 0.1mm layer height.  I printed this with a 0.4 nozzle, but it would probably look better with a 0.25mm or 0.2mm nozzle.   I found that printing at 100.5% yielded a better fit for my keyboard. You may need to do some experimentation to get the best fit for your keyboard.