Thanks to Facebook Friend Andrew for this tip! Connect with HBF on Facebook – Here
Stainless Ball Lock Carbonation Cap for $10.60 via Ali Express. Shipping for the first one $3.06. Each additional ships for less.
Check it out – Here. Note that this ships directly from Asia.
Use this to carbonate your beer in standard PET 1 and 2 Liter Soda Bottles or fill 1 and 2 L Bottles from your kegerator and use this to pressurize for easy transportation.