Boyds used to offer a walnut replacement stock. I just checked their sight and no longer see it listed. A call to them might turn something up.
If price is of little concern Wenig Custom Gunstocks out of Missouri lists the 44 carbine as one of their available patterns. You could get it in any wood your checkbook can afford. Going this route you could get a much nicer sporter style stock with a flat butt and recoil pad, way nicer than the factory curved butt in my opinion.