Remixed from Molak34's design for later-generation IntelliMouse.

Remove perished rubber from mouse wheel until you're left with the hard plastic structure underneath. You can stick something narrow in the holes to get rid of perished rubber from them as well, though it's not mandatory.

Print two of these wide side up. If printing both at the same time, do an "individual object" print - they are very short so any printer should be able to do one and then the other in the same session. Printed traditionally you'd probably get stringing and annoying bits to clean off from the wheel surface.

Slightly sand the mating surfaces with fine grit, then glue to the plastic structure using a dense adhesive with volume. I use neoprene glue; don't use superglue or similar runny adhesives as they won't fill in the space inside. Make sure there aren't any glue strings (almost inevitable with neoprene) in the digitizer wheel.

Let dry while lightly pressing the halves together. Reassemble. Scroll away into the sunset.

I printed these in PLA; I suppose TPU would feel more original but I didn't care.

No need for supports or brims. Final material cost about 1.2 gr.