2. Does anyone
have any light pens for sale or trade?
No, but it's not hard to make one if you don't require high resolution.
There was at least one design in 80-micro for the Tandy 1000. There were
plenty of designs for the Beeb (most of them use the Honeywell 'Sweet
Spot' devices). Thoese were not as good as the Torch one I mentioned, but
they do work.