Pinotguy, Dan Pedersen makes the correct .333 barrels. Here's his website: http://www.cutrifle.com/index.html
His stuff's good, but a bit pricey.
If a CZ or a Mauser is the only reasonable way to go, I could save-up the money for one. But, that reduces the money I'd have left for the gunsmith. I don't want to half-ass the rest of the gun.

Speaking of interesting actions, I did come across a nifty Mannlicher-Schoenauer action, complete with rotary magazine. But, I'm guessing that it would be too small for this cartridge?