I heard that you can order replacement parts from them through the phone, and it does not seem to be too expensive: a forum post on an airgun site said that a 24-inch barrel was only $12 (don't know if that includes shipping) and the crosman custom airguns section lists the price of a 24 inch barrel as around $8.

I know I can use a 4.5mm ID pipe to make a smoothbore barrel, but if a rifled barrel is available for that little, I'd much rather get that.
I would like to get a 24 inch barrel in .177 and .22 caliber if available. What are some airguns that have such barrels so I can try to order the barrels as "replacement parts".