Hello, the barrel thread is 1/2 x 20. So if you don't plan to use the factory shroud and prefer to screw the suppressor directly to the barrel, get the .25 KOI with 1/2 x 20 Cone:
https://donnyfl.com/collections/ldc/products/1-22-x-7-inches-koi?variant=6604174360615
If you want to use the factory shroud, you'll need this adapter:
https://donnyfl.com/products/hatsan-qe-1-2-x-20-unf-adapter?_pos=2&_sid=1e7235749&_ss=r
Then I would pair it up with a .25 Tatsu 1/2 x 20:
https://donnyfl.com/collections/ldc/products/1-6-x-4-25-inches-tatsu?variant=10542670676011
The .25 works great on the .22 but also reduces the chance of pellet clipping.
I would then pair them up with a .30 Sumo 1/2 x 20. 1/2 x 20 is the thread size.
The .30 works great on the .25 but more importantly reduces the chance of pellet clipping.