This achievement is currently bugged on the newest patch, at least it was for me. So it was unlocked in-game, giving me the ability to buy bombs at the start of a run.
So to get this achievement now, you have to go to properties on your steam page under the game, and choose game versions and betas and then choose 1.19.5
I used the following seed Hard 2006915028 PB. If it is the same seed you should find 4 bombs in the shrine of the green god in floor 1. I had found my 12 bombs by floor 6, on the floor with a lot of purple gas, flame turrets and a hidden room of mist.
Good luck.