Lever guns in .45 ACP seem to be an obvious choice, because you can rechamber a .45 Colt revolver simply by replacing the cylinder (or using moonclips if the design permits them), and turn a whole lot of rifle casing into .45 ACP brass simply by cutting them to size, so in theory a lever gat in that calibre would be a great companion gun. And yet, it looks like only a few small shops in the US make them by modifying .45 Colt guns.