880SQ Help

I have an 880SQ ,and i need to locate a new Barrel.
During A recent move i had to store my 880s in a storage unit. While in the storage unit, some small critter/insect decided to use the barrel as a nesting spot. About halfway up the barrel i found that it was blocked with dirt. After cleaning out the dirt i found that where it was plugged, the bore had rusted.
This gun use to be a 1/2 " @ 50 grouper gun, now it is about 11/2"@50 . I would really like to locate a new barrel for this gun.
I called Marlin, but they said that they would not sell me a barrel and that i would have to send them the gun, so that they could replace the barrel. I dont want to spend a fortune on the gun, but i would like to get her fixed.

Thanks

Bill