FYI nitrogen is not the same as nitrous.
If you want the creamy head but don't have a stout faucet, just carb to a relatively low level then serve using your creamer faucet. In a stout faucet/beergas setup, the nitrogen is only there to provide extra force to push the beer at relatively high pressure through a restrictor plate. It doesn't absorb into the beer. If you use CO2 to provide that force, the beer would overcarb, hence the nitrogen. So kegging with beergas or N2 then pushing with CO2 would simply dilute the headspace with nitrogen after a few pours.