Heart Stamp

thingiverse

A simple stamp with a heart motive, might also be used for a defibrillator. See https://github.com/ModischFabrications/Iconset-Modern-Medicine for a few more icons in the same style. The stamp has a diameter of 42mm. 3D-printing the stamp itself is certainly possible, but it's not going to work as good a you think it will. Trust me, even flexible filament is not that nice. You can try and sand it a bit to allow it to pick up the ink a little bit better, but I wouldn't bet on it.