Standalone CO2 assembly?

Got a question for y'all.

I own an ASG TAC6 and the main problem is: The dumbass moving barrel assembly.

I made a different post to see if there is a way to work around it, but I also want to see if there is a standalone CO2 gearbox/assembly anywhere to replace it, in order to get a fixed barrel.

The current assembly is somewhat similar to CO2 handguns, though without the CO2 cartidge in the mag