There are three doctors at UTSW who claim to have interest in LEMS. Trevedi, Nations and Phillips.
I go to University of Florida, Shands, Jacksonville. And while my doctor is not what I'd call an expert, he has had as many as ten LEMS patients and approved to prescribe Dap. He does, however treat me very aggressively, trying to restore me to as normal as possible.
Your own doctor can go through the process of being approved, if not already, but I understand it is a lengthy process with a lot of paperwork.
To find an already approved doctor in your area, Kathy Ales is with Jacobus, the manufacturer of 3,4 Dap, and is the coordinator for the DAP trials. You can give her a call or email her. Contact: Kathy L Aleš, MD 609-921-7447 ext 238 kathy.ales@jacobus-pharmaceutical.com. I understand she is very friendly and helpful.

This may not necessarily get you the Dap, but will put you in touch with those familiar with LEMS and how to diagnose and treat it.
Best wishes for you to get some sort of treatment back in place.