Talked to Fox Ridge Outfitters today about this very thing, and the short answer is YES, you can get one from them. As for length, blue or S/S, give 'em a call.
If you want performance data I'm only familiar with a load I worked up for a magazine article a few years back. Use 2 50gr. equivalent Pyrodex pellets, CCI 209 shotgun primer, .44 magnum Oregon Trails hard cast 300gr. flat nose bullet, (which is actually .429"), and a T/C sabot sleeve. Through a .50 caliber 14" Contender MZ barrel, I got an honest 1360 FPS over my chronograph at a local range. The equivalent of a .454 Casull Field Load. Hope this helps.
D'Keyman, Non Sibi Sed Patriae, (Not Self But Country)