Light pens?

I have two IBM Model 5150s (one original rev, and a rev b). I think I've explored every single inch of the hardware except for light pens -- I would really like to experiment with one and write some software that interfaces with one. Does anyone know: 1. What light pens were available and for which PCs? (I also own Tandy 1000s, and they have "light pen" ports too) 2. Does anyone have any light pens for sale or trade? I've already tried googling and searching usenet -- the only references I can find are companies selling light pens for modern machines, and tech info that states the obvious (ie. "The IBM PC supported a light pen"... yeah, thanks :-) -- Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/ Want to help an ambitious games project? http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/