I posted my problem with my leaking pump over a year ago. I just been riding it with it leaking. Not bad just annoying. So this winter I decided to get it fixed. I pulled the pump and took it completely apart. Not knowing what I was doing I removed the drive gear from the pump shaft to pull it out of the housing. Big mistake! The small pins and springs when flying. I did find them to my relief being they are unavailable and got it back together. I replaced all seals including the one inside the pump that’s not listed in the parts diagram. I only could find it at Granger  Item # 53XC09 and ebay but it was double the price. Only difference was it's a double lip seal original is a single. It went in no problem. It didn’t appear to be leaking.In the mean time waiting for the parts to come in I found that the shaft that the thumb is attached to has what looked like a epoxy plug in it. It has detached at some point over the years and was causing what appeared to be the seal behind the thumb wheel to leaking.  I removed it and put it back in with high temperature silicone sealant. So far so good!I hope this helps others that are having the same problem and remember be careful not to remove that drive gear!

You're more into it than I've ever been. Thanks for the info & update.