I know you weren't asking this, but just some food for thought, your brass options will be better if you go with either 20 practical or 20 tactical. I am smitten by the 20 cal myself, and have a 204 ruger and a 20 practical, and if I were buying a custom barrel I'd go 20 prac or tac every time. The brass is super easy to make, the downsides, if they matter to you, are no head stamped brass and no factory ammo. I reload everything and am careful with brass so neither downside matters to me at all. You can either get 223 range brass real cheap, or buy Lapua brass if you want top notch brass (also many other 223 options). 204 Ruger options are fairly limited.
As far as the barrel manufacturer, the ones I'd look at were already mentioned. Preferred's prices and lead times have gone up noticeably recently but still probably one of, if not the best value for a shouldered pre-fit. 405 bucks shipped for a threaded with shoulder, chambered and contoured barrel is pretty cheap. FWIW, I have a Preferred barrel for my Origin as well and I like it a lot, it's not a 20 cal though, haha. On another thread it was noted Preferred does not hand lap, so if that's important to you then look elsewhere.