Gunstar UK - 895 pounds - $1,500 Cdn. That is inexpensive if the tubes are any good!
24 bore = .58 rifled w/good bore it says
28 bore = .54 smooth

way too much drop, though.

https://www.gunstar.co.uk/american-kentucky-form-side-by-side-muzzle-loading-percussio/rifles/996543