Since I've recently more than doubled the size of my Systainer collection, I've decided that I don't like storing them on top of the vac. Instead of paying a lot of money for a Sysport (and I would have needed 2) here is my solution.
The carcase is 3/4" melamine which I had left over from a cabinetry project I just finished. I used Dominos (unglued) for alignment of all the box parts and held everything together with Confirmat screws. The drawer slides are from Gliderite and I definitely would use them again--including shipping a box of 10 sets was about $50, so the slides for this project were only about $25. The drawers themselves are leftover 1/2" baltic birch with leftover 1/4" melamine covered MDF for bottoms. The fronts are (you guessed it) leftover 1/2" MDF. I splurged there for a quart of color-matched paint in Festool green to make it fun. The casters I have on it for now are inexpensive ones from Harbor Freight that I had around, but I plan to replace them with some locking casters later.
Edit: I need to add that all of the ideas for this were shamelessly stolen from a thread over on the Festool Owners Group site where several members have made their own Sysports.