I used to get mine at Bob' Closeouts, but he ran out. I'll have to check the other places listed.
Always learning something on this place.
I built a ammo locker out of a used gun cabinet (good ol Craigslist) and some Home Depot clearance lumber. (I hope to replace with metal at a later date) Total investment around $50. Figured if I was worried about moisture, it could be sealed and a dehydrator added.