Ok I have a hairbrained idea, and thought I'd run it past people who should know better!
It's my understanding that as a homebrewer it's difficult, if not impossible, to bottle a nitro beer and not have it seem flat when it's poured later. We need a widget. Commercial nitro beers, add a small amount of liq N2 right before bottling, which raises the pressure in the bottle and forces the beer into the widget, then when the bottle is opened, the beer escapes the widget, foaming and causing nucleation sites for the rest of the beer.
What if we reused bottles with widgets in them? I may not have ready access to liq N2 (actually at work I do, but it's a logistics thing), but we could add a pellet of dry ice, or maybe if the beer was over beer-gas-carbed to begin with, that would suffice.