There are a ton of brands and I got a random knock off so I can only report on that one. I would recommend putting some thought and research into what size you think you'll need. I got a 58mm printer and I'm realizing it's quite narrow.

Also you might want to consider the size of the printer itself. I bought a open-box new printer off ebay and the seller's photos didn't give any sense of scale. I was surprised how big this "mini" printer is. It's about the standard size of a printer you'd see at a grocery store, so I don't think I'll be keeping it on my desk.