you would be better off buying new as it would end up costing about the same.
why dont you like the carbine? you lose very little in velocity(50 to 75 fps) and accuarcy can actually be better and the handeling of the carbine is far slicker & quicker. haveing a tube that is 3.5 longer isnt going to give you a noticable gain in performance on a 30-06 hunting condition http://www.chuckhawks.com/rifle_barrel.htm

I recently Heard that ellwood epps does rebarreling on 7600s in various calibers and aftermarket barrels they are the only folks in Canada doing this as far as i know. http://www.ellwoodepps.com/

If you just want a factory replacement tube then a local smith could probably do that for you but again it would be as much as a new rifle.
http://www.e-gunparts.com/productsc...Model=0860z7600

accuraccy systems does custom work on these rifle but they are in the states.
http://www.remington7400.com/index.php

I have had a 7600 carbine backordered for 7 months now