Advantage Arms
www.advantagearms.com also has a similar .22 LR conversion for various of the Glocks. I got one for my Model 27. It's not a bad compromise since .22 LR rounds are nearly free compared to .40 S&W rounds. The TSG unit displayed looks good. Only problem with the Advantage Arms conversion is it's made in Kalifornistan, and a 10-round magazine is the largest they can sell. It would be a lot more fun to shoot with a larger mag. Weight of the slide is somewhat lighter. Weight of the mag is considerably lighter, so there is a noticeable difference. Still, I shoot my Glock more than I would if I was feeding it a steady diet of .40's.

For your consideration,
Crusader