Lyman would be the only source of a barrel specifically for the deerstalker, you'd need to contact customer service.
Green Mountain "drop in barrels" for the T/C will also fit the deerstalker but will be longer, 28" or 32". Although they are called "drop-in" they often require a bit of fitting even on a T/C rifle. Also, the 28" barrel for a Lyman Trade Rifle or a T/C Hawken can be fitted to a deerstalker.