Most decent hardware stores have pint and quart cans. You want unlined, non treated cans. Check auto paint stores also. For your thinned clear, I would use the 8 ounce jars that fit the simple, single action Badger air brushes and some others. It's the same size jars that SIG, and Brodak dope come in. It has a decent seal and can easily be reused since it's for clear. Mix up as much clear as you think you will need for a project, then put it into the smaller jars. Use the pint and quart cans to hol raw dope, or to store larger quantities of thinned colors or clears that you won't need for a while. If full up top the brim, the less air there is inside the longer it will keep. I'm sure there are on line sources for these, and local ones also unless you live in the sticks.
Type at you later,
Dan McEntee