Try this for an alternate source for that adapter:
CO2 Regulator to Nitrogen Tank Adapter
They work fine!
Most people force carb with CO2 and then switch to beer gas for dispensing.
You can go the carbonation stone way, but more hassle I think.
Straight NO2? If you use nitrogen dioxide for anything, you won't like it!
I assume you meant N2. I have read that it will only work for beers carbonated to less than 1 volume of CO2.