H&R has made combos in the past, and they have a couple currently, but not in that configuration. The only way now for a new one is to buy the 223 or 308, then send it in for the other barrels. They may not have any muzzleloader barrels left, the Huntsman was discontinued a couple years ago and they may be doing away with them completely in the accessory barrel program, so you should call ahead and check, and if they do, get it right away while they have them.
An alternative is to buy the barrels used and fit them yourself, barrel fitting is covered in the FAQs and Help sticky, sometimes they fit fine, others may need some changes to fit.
Tim