Freewheel Gates Carbon Drive for belt alternative

I am going to convert a single speed bike to a belt drive.

1. I understood that I had to split seatstay.
2. I'm going to change the chainring/bracket for belt compatilibity
3. For the rear cog the only reference seems to be a Gates Carbon Drive freewheel : https://www.gatescarbondrive.com/products/rear-sprockets/22t-freewheel-cdc

I'm French, I have the impression that it's only sold in the USA and it's very expensive. Do I have a screw-on freewheel alternative ? I don't have a freewheel on my hub and therefore I don't want to change the hub or the complete wheel to fit with 9 spline rear cog.

https://preview.redd.it/580i8r7e5wud1.png?width=490&format=png&auto=webp&s=7509d00545a7ac4aaf948d3d2f9c2d22b29b99f2

Thank you for your light !