I thought an eraser could work well as a rubber tip but it didn't turn out as well as I'd hoped.
This uses an eraser from a Ticonderoga NO.2 Pencil. Cut it from the base with a razor and slot it into the performance tip. make sure you slot it in with the rounded end facing outwards. A dot or two of super glue in the tip is recommended but not necessary.
The author remixed this model.
I created a tip that an eraser could be inserted into.