Can't help you with sourcing any, and it looks like you've managed to find a (more than) suitable alternative, but here's a little known fact.
They are actually pre-molded 2 litre soft drink bottles, called "preforms". They get shipped to Schweppes/Coca-Cola/etc by the pallet load, who then heat them up, and add a controlled amount of hot air inside a mold, forming the PET bottles we all know.
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