It's possible to make implantables with some banks through the same methods as wearables, which is pretty convenient. Otherwise, the option is to take your card and (assuming it's of the correct type) cut out the chip inside and coat it to make it safe for implantation. I'm aware of at least one business that offers turning credit cards into implants as a service. Cloning is pretty much a no-go as you suspected.
Can it be done with some kind of reprogrammable chip? I could see myself getting the surgery once, but I definitely don't want surgery every 3 years every time the expiration date on my card resets (or whenever I change banks, etc)
You would need not only to cut out and implant the chip itself, but the sizeable loop antenna that runs in a rectangle close to the perimeter of the NFC card. It'd be a hassle!
My understanding is that it depends very much on the card. Certain ones can be done more or less with just the chip, others are much more involved, and others can't be done at all. From my brief research, there is a lot of technological variation inside credit cards, even if they mostly all look the same on the surface level.
