Not sure if you're interested in it, but I was looking for an integrally suppressed CZ but it was 41F time and I wanted to get it in so I got a Liberty Pinnacle 2 for a 10/22 I built. Anyway, I believe it was Thompson that had a large selection of integral barrels including the CZ but you could also look around and even get custom made integral barrels if you wish.
FWIW, the 16" Green Mtn. match blank they bored out 12" to accept a long monocore left 4" or so of barrel. Despite this, it's still very accurate for a 10/22, so far ~1MOA at 25m first time out just farting around at a birthday party in the back yard but there were some ragged single holes too. Some from prone, some standing. I expect it to do well at the range later when I have time alone with it.
A CZ would have been quieter with the bolt action and probably more accurate.
Sorry if this isn't up your alley, just thought I'd mention it. Good luck!
If looking for a good long barrel though, my first thought would be to call all the best mfg.'s that I like to see if they do it, then go from there.