Top row Cherry MX keycap with a simple exclamation mark.
This should be compatible with any keyboard using a cherry MX switch, and the shape is to match the top row keys.
Note that my images are taken with a Non-RGB keyboard with a white backlight, the only colour is added by the keycap.

Note this was printed on a resin based printer, I'm not sure how well FDM would work, feel free to try it.

For a blank Cherry MX keycap see: https://www.thingiverse.com/thing:3139161

See my other keycap designs on my page.