We have not had much of a request for this part. We did recently start making this part:
https://www.kegland.com.au/premium-...mfl-grey-gas-with-integrated-check-valve.html
We obviously have this one but I assume you know that already:
https://www.kegland.com.au/duotight-8mm-5-16-x-one-way-check-valve-non-return-valve.html
So the only check valves that will screw directly into the regulator body at this stage is this one:
https://www.kegland.com.au/1-4-inch-ball-valve-with-check-valve.html
I must say it's not something we get asked for much so we have not designed and have no plans to make a duotight fitting/check valve that screws into the regulator body.
I personally don't really like using a check valve between my regulator and kegs for a couple different reasons:
1. You get a small pressure drop over the check valve. So when i set my regulator at 12psi for instance, the check valve will drop the pressure to about 9-11psi. I dont really like this fact but that's simply how check valves work. They have an opening pressure that the gas needs to overcome in order to work and this results in a pressure drop.
2. Clearly you can sometimes in be in a situation where the you relief gas in the regulator side and then as the pressure is lower the pressure gauge doesn't read the actual pressure in the keg anymore.
So although I recommend beginners to get a check valve I personally just make sure I am a bit careful and i prefer not to use one myself. If you have a bit of experience and you are a bit careful you can easily get away without a check valve.