Yep, Scott is right, they are not true "Lightguns". They just an x/y controlled via pots.
As for mine, I bought the entire machine at an auction. There is a complete set of guns currently up on ebay for $90 + 25 shipping. Only one is pictured, but it is both included in the listing. I'd link it, but I don't want to promote the listing in case you are seriously interested.