The D2 Charlie is based on the Fenix 5X so any band that is available for the F5X will fit the D2 Charlie, which means you need a QuickFit 26 compatible band. Garmin doesn't sell a black leather one but there are lots of third-party bands available on Amazon and such so it's certainly possible, though once you sway from OEM your mileage may vary.
Another alternative would be to buy the Garmin leather band and use a dye/stain to darken it.
