I don't know of anyone off hand but it's likely the barrel would be on the expensive side. You would probably be better off to buy a fixed choke barrel, have it cut down to the post closest to 24", and have the barrel threaded for chokes. At the most, you would probably pay what a new barrel from Remington would cost depending on the price of the barrel and who did the threading.
Yes sir, I sorta figured that would be the answer. Now to find someone to send it to, any recomendations?