The 1/2 gal. ones are pretty rare these days. Mostly found in antique and collectibles shops. Best source of finding any large quantity of those may be estate auctions, ebay, and, sometimes, if you're lucky...yard sales. I have a few of the blue ones that my mother gave me, along with the galvanized lids. I use them to store dry goods, spaghetti and such.
I recently found some at an auction. I too use them to store dry goods such as rice and pastas. They look pretty sitting on the shelves in the pantry! Remind me of my Grandma!