I saw something similar once but couldnt find it, so i made one myself.

Depending on your printer, you might want to cut off 1-2mm on the tips, so every arm has the same length and tip-size. sometimes the tips dont get printed well, because they are too pointy

I marked the edges with a bigger D20 and placed the tentacles accordingly, so that every side has the same size. this should give you a well-balanced dice-feeling (i hope i didnt screw anything up :P)

There are now more printer-friendly versions of a D20 and a D6
https://www.thingiverse.com/thing:4422453
https://www.thingiverse.com/thing:4421807