I know that you can now buy Co2 mags for the GHK Glock, but I have my doubts about how the pistol will cope with the extra pressure. Samoon do a Co2 kit which I purchased unfortunately. Parts of the kit are good, like the steel inner barrel & hop chamber & steel rails.
The Co2 mag was poor, the valve was rubbish, the supposedly Co2 rated nozzle was damaged after a couple of capsules.
I have no doubt the Umarex Co2 mag will be good quality, but the pistol is rated up to 150 psi, Co2 is around 800 psi I think.
Spoke with the tech at patrolbase about using high power gas in cold weather as they recommend on there website, he said only use black gas when it’s very cold, so how it would cope with Co2 I don’t know.
There is a S/H one on the forum at the moment for £295. I know the seller and can guarantee it’s absolutely as new, probably only been test fired, if you don’t want to buy a brand new one at £370.