Don’t think you’ll find a stock one in the UK, plenty of HK retailers will have them though.
As rocketdogbert said it will most likely be over UK limits on standard green gas, I have an upgraded WiiTech nozzle in mine and need to use 134a to get it under 350fps.
The new Vorsk VP1 *may* have the same system as the MP9, so maybe a nozzle from that will be compatible….