Unless you happen to have the exact same kind of pepper grinder, and you are looking to repair the exact same plastic piece this will not be very useful to you. The main reason I am uploading this model is to document the stuff that I managed to repair with my 3D printer.

The (gray) plastic piece in question connects the body of the pepper grinder, which holds the grains, with the knob at the top that you turn. It has a square hole to hold the grinding axle, vertical grooves to hold onto the wooden knob, and flexible hooks that snap into the hole of the body of the grinder. It was those hooks that broke in the original piece.

I drew up the model in onshape. I printed with (black) PLA, although maybe PETG would have made a more resilient and therefore longer lasting piece. Layer height is 0.1 mm. I printed the model with the flexible hooks pointing down and resting on the build plate. Supports are necessary due to the overhang.