None from H&R as an accessory barrel if it's a factory VP, as far as I know they won't fit any barrels to a VP frame, but it wouldn't hurt to call and ask in case they've changed their policy, they'll need the frame serial number. As for fitting your own barrels, shotgun and low pressure chamberings will work, 357 and 44 mag, Hornet, 30-30, 45-70 trapdoor for examples.
Tim