Uggghhh. My stepfather is actually one of the very vocal folks regarding the issues the VA has with taking care of veterans. I do thank you for your service, and can't believe some of the hoops you guys have to jump through.
Unfortunately, I don't know how Medicare works in this case, but if I recall correctly, the VA does allow you to contact NON-VA docs if your wait is in excess of 90 days. I don't know all the logistics behind it, but it sure sounds like you qualify, ESPECIALLY given your VA doesn't have an endo.
I'd have a good talk with the patient advocate and see what they can do for you. (I think that's the title, it's been awhile since I have had the run down on how this stuff works as I'm not a vet, it's a long story, but my size in 1993-1994 was too big for the armed forces, except the Marines - which scared me off). Hopefully they can find you a time slot MUCH sooner and to your liking.