The only 17hmr barrel that will work on it is another Versa pack barrel which Gander or someone has made, I think Kurt has one, it requires an offset bore to work with the Versa pack frame which H&R won't fit any other accessory barrels to unless Remington has changed their policy, Gardner wouldn't, but they do work with other shotgun barrels if you want to fit one yourself, see the Versa Pack sticky.
Tim