Before you do, let me forwarn you and also wish you better luck than I had.
Seems that we don't seem to have a lot of APS format users (or at least not at the stores I went to ... not even a Wal*Mart.) Our neighborhood Ritz said they use the containers to hold the negatives when they return them to the customer. I hope you have more APS users in your neck of the woods.
The first time that I checked was about 3 years ago when I first read about APS containers here, and then I checked again about a month ago without success, but I haven't really been looking all that hard.