HP 41 card reader repair question

[DeeVeloper]

I am repairing the hp card reader and have found the worm drive gear was slipping on the motor shaft. I removed the worm gear and cleaned out the aluminum tube. Now I need to know
--what can I use to back fill the tube with and
--how do I adhere the gear back onto the motor shaft ?

I tried to use wire insulation to fill the tube but can't find anything that fits.

thanks for any help