Thank you everybody! Problem solved!
Scott, thanks for recommending Dan at Explorer Dome. He was very helpful, and led me to the right place on their web site. At first all I saw was their small domes. but hidden in there are many pages of info and parts.
I got my gear rack and main gear for a very reasonable price. they also have the rest of the parts to finish the job if you don't want to make them yourself.
The gear and rack are made with poly-something. When I asked about durability Dan said that they come with a lifetime guarantee. That works for me. Here is a link
to the page of their web site I was on. Yes, it says it is for dome rotation, but the rack comes straight and has to be bent to rotate a dome.
You can check on the other thread
to watch the completion of the dome over the next month or so.