Are you wanting metal or plastic? Walmart has the plastic ones for $5. The metal ones I only seem to find in Gander Mtn and one local gun shop and the go for $15 at the gun shop
Gun shows, craigslist or forums are where I have found the best deals aside from once in a while crazy deals at one of the big stores (and those are few and far between). I know you are looking for local sources, but keep an eye on some of the online surplus places like cheaperthandirt or sportsmansguide. I just scored a bunch of .50Cal cans for $8.99 each with free shipping.
Not sure how far you are willing to drive, but Delk's in Asheboro has a big selection of military ammo boxes and other kinds of military containers. Delk's Army Navy Surplus_Home
Figured I would pass this along, Outdoor Limited is having a big ammo sale this weekend. They are a local NC company in high point and I've ordered from them in the past without issue.