Drivers and cannoneers in Battery F, 1st Rhode Island Light Artillery (and other batteries in the New Bern area as well) were issued pistols rather than sabers.  The Ordnance Returns show that, to carry them, they were provided with standard infantry privates' waist belts rather than saber belts.  If you need a plain old US belt with a standing leather loop and plate appropriate for the time being portrayed, here is one from Merrick's Custom Leather.