I think your best bet is to talk directly to your insurer, you need the specs of your policy to know for sure. My vendor couldn't bill them directly, but I did get reimbursed for one of mine.

Also, B2, I would discourage you from buying your first one from an internet seller. There are many styles/types of rollators and this is something that you need to test drive to be sure it's what you need and want. Your vendor can help you with adjusting it to fit you properly and give you tips on using it to your best benefit. They'll also do those occasional tweaks and little fixes for you.