A possibility is the AAC Evolution-40. They sell their Evolution-9, with a fixed spacer to replace the recoil booster, as a SMG can. I don't know if they will rate the .40 version for 10mm, you'll have to ask them. You'll need the recoil booster to cycle your pistols, of course.
As for barrels, for the USP, you could get a factory barrel, which is threaded 14.5x1 LH. Jarvis Custom also makes such a barrel. Jarvis makes barrels for the 9mm P99, but he doesn't list one for the .40, but the name does say "custom."
Hopefully these ideas will get you started.
BTW, I'm interested in hearing about your 10mm AR. Is it gas operated?