Welcome NewGuy!
Lots of tin containers around to recycle; althoids, Fishermans Friend, tackleboxes, tobacco containers, gun cleaning kits, candy/cookie tins, etc.
You may have the right idea about starting out new with the right sized container, as I am overrun with ones I have scrounged.
Some nice containers can be found on retail Survival Equipment websites like this one
http://www.bepreparedtosurvive.com/Misc.Conatiners.htmGood Luck, building a PSK can be a lot of useful fun.
Mike