If the PLA is using it, it would suggest to me that there is a Chinese company somewhere making them.
The PAP has no issues buying off-the-shelf, but it is extremely rare for the PLA to field things they cannot make themselves, and lets face it, the FAST helmet is hardly beyond the capabilities of numerous Chinese firms to make.
In a way, I kinda see the PAP as almost performing a field trials service for the PLA. They buy all the newest foreign gear with a law enforcement purchase order, and the PLA will undoubtedly get to play with anything they want from the PAP inventory. If the PLA kinds something they like, they will probably task a Chinese company to make a copy or something based off of it.