I can confirm that the offgamers method of buying a mint card worked for me.
1. went to offgamers / signed up
2. bought a 30$ usd mint card
3. after they verified go to order page and the code will be there
4. copy it
5. go to pixel gaming website, login, go to purchase, click paymentwall/MINT clicked 30$ usd
6. It will ask for a mint pin and you paste
7. done
(I tried buying a Mint card right from the Mint website but they said they didn't have any for my region (US).