I had one of those, way in the wayback days. It worked as well as one could expect.
Is was when we figuring that stuff out. Some games didn't work but lots did. For less than $10 you can't go wrong.
The only cavet would be that the publishers may have done things to break that functionality. YMMV and it could be the image. Certain games had to be juggled others didn't. I seem to recall you could write an image and it would verify, yet the game wouldn't load.
I think the only existing devices would be the ones that work. I can't imagine the market is hot enough to support fakes.