I have a Duo unit I'd trade for it, but you wouldn't want it. It was bought new by me a few years ago, has less than 40 hours of use on it, and its already not working right. In other words, if your going to give up something as valuable, and good as PDS, make sure you get something decent for it. Duo's are unreliable, cheap, crappy units, and even though I'm proud of mine (even the 3 dead ones I have) they just weren't made very well.
Oh, and I already have Panzer Dragoon Saga anyway. Bought the last one at a local Toys R Us store when it was on closeout for $20. Good deal in my book