The original (black) Duos are starting to fail in pretty huge numbers. The Duo R was a later version that (for now) seems to be a lot more reliable. They are white, a little thicker, and lack the headphone jack. The Duo RX is another version that is the same thing but with a 6 button pad. Just get the R.
As for where to get one, there are a couple of guys on this forum that do mods, they might have one. The units themselves are all over eBay.