I would like to buy a game to send it as gift to a friend. This is a Secret Santa though. It should be anonymous. I would like to buy legally a key on steam or any other official seller (like humble bundle). Print this key of a postcard and send it by classic mail. How can I achieve that.

If it matters, I am looking for:

- [There is no game : Wrong dimension](https://store.steampowered.com/app/1240210/There_Is_No_Game_Wrong_Dimension/)
- [Goat Simulator](https://store.steampowered.com/app/265930/Goat_Simulator/)

Related to (but not a copy because I am fine buying keys outside of Steam) https://gaming.stackexchange.com/questions/284460/can-i-buy-steam-game-keys-on-steam