The RAMI is unique to CZ's in that it uses a Glock style breach block, instead of a Browning style.
So there are no other CZ's to get a longer barrel from.
In theory you could machine one from a barrel blank, or possibly find another gun you could adapt a barrel from, but machining a barrel from scratch is a pain, and it is unlikely that any other gun with a glock style breach will be close enough to work.
You can use the same method I used to add a muzzle compensator to my RAMI.
You machine a small shoulder on the muzzle end of the barrel, and then machine an extension that slips onto that shoulder and then silver solder it on.
Not really that hard for a competent gunsmith.
Or you could use the method I used to extend a couple of 22 Long Rifle handgun barrels.
Drill out the bore of the barrel.
Solder on an extension piece and bore it out to match.
Machine the exterior of the barrel to match
Silver solder in a barrel liner, trim to length at both end and then rechamber for 9mm.
9mm barrel liners are really hard to find, but you could try Redman.
They make all of Brownells barrels liners.
http://www.redmansrifling.com/liners.htm