[Joe Sr.]

Here is the one that is on my to-do list.
http://www.brewgeeks.com/carbonator-cap.html

That's pretty much exactly how I built mine.  They work just fine.  I carb with the air chuck just like in that tutorial.  I have QDs on all my gas lines, so I can switch from pin lock to ball lock to air chuck to air gun or whatever quite easily.  I've also got a splitter I can swap in easily which is nice.