1979 RM125 Need kick starter idle gear

In 1981 I purchased a 1979 RM125 that I road for many years. I then left it at my parents garage for 25 years, I would ride it in there backyard every couple of years. When my kids got old enough to ride it I went and picked it up.
This bike always ran great. I now need a kick starter idle gear. If any one can tell me were to get one I would be very happy. Thank you in advance.
Tbrag