I got a used Stewmac fret hammer, and I immediately broke the plastic face during misuse. Stewmac wants almost $5 (plus shipping) for it, you have filament, download it and print it with any material you'd like.
I suggest printing with 100% infill, as you’re going to be smacking stuff with it. It’d probably be better to print with a more ductile filament like PETG or ABS, but plastic is cheap so it probably doesn’t matter.
The author marked this model as their own original creation.