If you really wanna nail your US impression for the first half of the war, adding a waxed flesh box belt is one step in that direction.  This waxed flesh is made just like the standard type of leather used for cartridge box belts and waist belts in 1862--rather than just the fuzzy flesh side of the leather dyed black, this stuff is oiled and waxed and slicked with glass to the smooth, glossy finish.  It comes with a cartridge box plate attached with the appropriate tapered strip of leather.