Sorry to hear about your luck.
One thing you might be able to do. I think we're talking about an XR400. If you can make it to a dealer there is a good chance he has a new or better yet a used XR400. This is a lot to ask for some dealers so bare with them. See if he can take one off. I believe thats an easy fix from the outside.
Also, are you using OEM springs or after market? MAny times after market are stiffer springs which most often is not necessary. Especially if the machine is not highly modified, which I doubt since your going long range. This may casue undue stress.
Also, if your using the clutch a lot you may consider changing your gearing. MAke it lower, more teeth on the back. This will get you in the power with out use of the clutch. Of course , on the open rode it may hurt you. This is often why people will carry different front sprockets. They are easy to change in a few minutes and you can adjust your gearing as you go.
Also, I'm very interested in the Trans Am trail. Once you get going let us know whats up. Get a blog I guess its called.