lathe dial

Hello everyone, I am new to the forum, I am sorry if I have posted this in the wrong section. Please could someone help me with making a thread dial indicator, the part that I am struggling with is making or getting hold of a gear that I can use on my Chester MF42-B. It has a TR20 x 4mm...

I just made a couple of new dials for my Logan lathe. The difference this made is amazing... the original are almost unusable (at least for old eyes). Tubalcain on Youtube has a video on how to do this although I did mine slightly different. I kept the old dial and made the new dial slip over...