The blue nozzle will probably be fine for a while on CO2. It will definitely break faster on CO2, but whenever it does, replace it for a red one and you'll be good. The nozzle is just an expansion chamber for the gas expelled from the magazine, you will still need a stronger hammer spring to be able to use the CO2 magazines.
You can order direct from KJW at
sales@kjworks.com.tw. If you are about to order the spring from them, you might as well order the red chamber at the same time. It might also be a good idea to order a stronger recoil spring too to help absorb the CO2 blow back shock.
Also note that optimizing a gun for CO2 will decrease performances on propane/green gas. The stronger hammer spring will release more propane, which will reduce efficiency. Also, the gun will cycle slower on propane due to the stronger recoil spring.