As told by Paul in the forum :
“The pinions measure 3.75mm OD and have 13 teeth. The shaft measures 1.55mm. I’m thinking that this is very similar to some remote control helicopter pinions I found online – 13T 1.5mm shaft mod .25 (101P). I’m going to check with a local RC hobby shop to see if they have anything, but otherwise I’ll try to order some of these pinions (http://www.xtreme-production.com/xtreme … ts_id=3013).”
Someone used pinions from a Sony CD player.
If you want to share your solution, please, contact me.