I have a ton of money in my Flex Spending Account that I need to use by the end of this year.

To use your FSA, I doubt very many providers here qualify. They all "say" they're CMT but rarely will they be LPT. Good luck.

... if you get a letter from your doctor/chiropractor prescribing regular massage treatments, you can get the massages reimbursed--check your health insurance policy about coverage.  Of course, you'd need a receipt to show your insurance company for reimbursement.  Probably want to keep the receipt amounts within a reasonable range--insurance company may look into it if you ask for, say, $180 for a one hour massage.

I have done this for monthly massages at a massage therapist (not a provider) and use my Flex Spending Account debit card for payment, and I haven't had a problem yet with insurance.  If they challenge it, I have my chiropractor's letter.

I guess the question would be if there are any providers licensed to provide this type of massage willing to provide the documentation you might need and also offer an erotic follow-on.

I didn't say it would be easy. I only laid out the parameters. The receipt, which is subject to verification, is the hard part. You'd have to know the LMT provider very well.  Alternately there are legit massage therapists who offer HEs; those might be the best bet for something like this.