I've got 2 DS50s I'm not using anymore. I might have a spare ball attachment, I'll have to check when I get home.
What are you looking to pay?
Not sure if I should go with the DS-50 or the DS-51?. Just looking for one. I would need to know a few things first. How old? How many dives? Serial Number? Any problems with function. Condition? What comes with it?