If you are not DIY skilled with building your own Gun4IR system, there are some people that sell completed packages - but they're expensive. ($400 US per gun is what I've seen).
Personally, I use Sinden guns on my cabinets (Windows). Overall, I'm happy with them. Little tweaky to get working at first, but afterward the initial learning curve, they've been great.
I am interested in Gun4IR guns, but I've got too many other projects going on right now.