Heck, if you live in a city with a techie population, then buy a bunch of cards, throw them in a bucket, then sell them for a 1% markup, in cash, at any tech meetup you attend. Buy more cards periodically and toss them into the bucket for people to pull at random, so there's no plausible correlation between time of issuance and time of use. This also covers your own tracks as well, if you ever need a VPN.

At least Webhallen in Sweden sells them in physical stores around the country. Not sure about other places though.

Weirdly enough it's also cheaper to buy a 12m card there (500SEK instead of the usual 600SEK). Checked, and they're listed as a reseller on Mullvad's page so they must've gotten a good deal / are selling at a loss.

You can buy them in some tech stores around Sweden. Don't know about the rest of the world.

If there’s a demand for it they can just get it off Amazon and mark it up.