Regarding the losing little black ring, I had been suffered for this a long while. Evetually, I am able to find the good replacement. What I found is Highland Barley paper 0.2mm is able to subsitute the black ring. What I did is cut the paper into circle shape, the use cutter to cut a very small hole in the center. Also, cut circle from the boundry toward to the hole to make the cicrle opened.
Then try to put the circle back to the axis to see if it fits. If the hole is too small, you can adjust a little bit until it fits.
For those of you suffer the same issue, and unable to find 0.2 mm or thinner highland barley paper, I can give some to you for free (yes, even you don't buy gears from me )
Just want to share the solution / happiness for finding the replacement.
Thanks
Jimmy