The only current offering in 357mag rifle is on an SB1 frame that can't be fitted with any other rifle barrels, you'll have to buy a Hornet Handi or a used frame, then have accessory barrel(s) fitted to the frame, or buy a second hand barrel and fit it yourself as shown in the FAQs. They used to offer the 357mag on an SB2 frame, but no longer do, so you may be able to find a used one too, just be sure it was made 1987 or later or they won't touch it with an accessory barrel. There are no aftermarket barrels other than from the accessory barrel program unless you have a gunsmith make one.
Tim