Could use advice navigating FSA/finances and physical therapy needs

My apologies if this is not allowed. I have been dealing with CDH and migraines for years. I recently became diagnosed with hemiplegic migraine which apparently means I can no longer use my previous abortive medications for migraines, which has led to significant worsening of pain and a decreased quality of life. I have increased my PT from once a week to twice a week and have also begun EMG and thermal biofeedback. It’s taking all of my time. I had to start working from home. My physical therapist has recommended I purchase some things to help with my therapy, but I am struggling with finances. I recently purchased a standing desk and walking treadmill for under the desk that I couldn’t afford as sitting all the time worsens my pain. My physio told me she could write a letter of medical necessity so these items could be covered under my FSA, but the FSA will only reimburse those items, not pay for them in advance. I have found websites like the HSA Store that have had things that aren’t FSA eligible anywhere else but can’t seem to find these items anywhere else. Has anybody here had any luck finding physiotherapy type items eligible anywhere with FSA/HSA cards? Here is an example of items. Obviously it can be anything similar to these. But I searched up and down the web and couldn’t find anything remotely like these that were FSA/HSA eligible and my PT doesn’t sell anything in house. Does anybody know how I can navigate this and get these items upfront with HSA/FSA funds?