I was at a local clown/balloon shop the other day to purchase balloons and I noticed they had a case gently used by a local clown on sale for $45, so I bought it. The case is a little deeper than my preference but it is overall the right dimensions (about 12x18). I really like the "traditional" or "old-fashioned" look of the case over the aluminum-sided cases that are so common today. Does anybody know of a good source for these in a variety of sizes? Please don't advise eBay because it is so hard to find just the right size on there. A clickable picture is below (the hat is for scale).

Try the second hand stores and Goodwill shops. Some times you can find trunks like that. If you are close to any of those places just stop in when you have a free moment and check it out. Try and talk to the owner or manager and see if they would call you if somebody brought one in.