The reason it's so difficult to get certified to prescribe Dap is that it is not FDA approved, mainly because LEMS is so rare and there are not that many people needing it.
Special permission must be obtained to prescribe it on a compassionate use basis. It has been provided free by Jacobus, a small family owned company, for upwards of twenty years. Usually the only cost is for shipping it.
There is another company, Catalyst, that is a publicly owned company, that is trying to get FDA approval for the same drug, only tweaked a little so that it doesn't have to be refrigerated. They are looking to charge exorbitant rates for this same free drug, claiming that is a brand new treatment.

We are all holding our breath waiting to see how it all plays out.
I hope you can get a treatment that works for you whatever it may be.