I can see why you need a new one. It wouldn't be an easy gear for an engineering shop to make one, with that piggy-back ratchet plate doohickie as part of it. It would probably have to be made in 2 parts (gear and index plate) and joined together.
Might be simper to fit electric start to the bike!
Hopefully someone will have a good used one for you.
What I was hoping was as this must be a common problem with early egg engines was that maybe someone had produced a short run of them and could sell me a new one. A friend of mine did attempt to make one for me but the profile of the teeth were not pointed on the ends and they had not got the spacing of the ratchet steps bang on so it was doomed to failure.
I live in hopes.