I have had some experience with low pressure pneumatic s with death warmed up/immortalis/metalis and I
sourced most of my rams from the barsnley bus breakers-they are only £10 each.
You don't get a spectacular launch with low pressure rams at heavyweight level, more like a steady lift but
they are a lot safer than full pressure which can kill unless you know your stuff and even the best have had
accidents.

Gas-
The smallest Co2 cylinder I believe was the 2 kg but I'm sure they discontinued the short stubby cylinder
in favour of a longer larger capacity cylinder which is no good when space is a premium but you can still get
hold of them second hand but you may have to get them pressure tested which isn't a big problem.
https://www.ebay.co.uk/itm/2kg-co2-f...kAAOSw7upcqE21
Another alternative could be paintball equipment,cylinders/regulators -they are certainly smaller but the
amount of gas would be limited.
This will require careful consideration Andy, if you go to an event with full pressure flippers like Apollo/iron awe
ect and you have a low pressure flipper you will be outgunned unless you can learn something from the behemoth
team-the most successful low pressure lifter ever.