I'm happy with my current method of making caps, but I think I'll get one of these to play with anyway. Thanks for the heads-up!
I agree refilling a 2L bottle from pressurized CO2 wouldn't work. At 90PSI, CO2 is still in the gaseous state, which is FAR less dense than CO2 in the liquid state as found in a pressurized tank at 800PSI. So it really won't hold much CO2. And as you use it, the pressure would constantly be dropping, so you'd need a regulator to ensure a constant flow - for a setup that would probably run less than a day. Plus, while a brand new soda bottle may reliably survive a one-time pressurization to 90PSI, I definitely wouldn't do it on a day-to-day basis!
But this has me wondering about something else. I've heard you cannot drive an "atomic" style diffuser with DIY. Why not?