2 liter soda bottles would probably be your easiest (and fairly cheap!) option.
The only thing is, with bottle conditioning you only want to open a beer as big as your glass. That's because the act of pouring, up and down, will resuspend any yeast sediment so you'd have 2 liters of beer that has to be consumed at one sitting (due to oxidation) and poured into a pitcher first
What is the largest bottle I can use for bottle conditioning? I have a batch that will be ready to bottle before I purchase a kegging system. Trying to cap as little as possible. Thanks
If you prime in the keg, it seems to me the Co2 would begin filling the head space?