The eBay seller is called bidnizz, and I think he makes them himself. I don't know if I am allowed to post his eBay store on here since I'm not him, so I won't.
Sure, they're a bit rough and ready, but they cost $13 (not including shipping), so about half the price of a Hat Jack. These are also much thicker than other stretchers I've seen - basically the same thickness as the ribbon on your fed - 1.5 inch or so. Plus they don't have a lip on them you have to take off with a Dremel. For that price, if they aren't quite the shape you want, you can just have a go at them on a belt sander.
Anyway, I thought they were a good deal, and if anybody else is looking for a cheap stretcher, they seem just fine.