Well, judging by how well it takes the stamp, it's veg tan so it should be susceptible to hardening due to heat. Wet it through, wrap the gun in saran wrap and wet mold it around the gun, remove the gun, then toss it into an oven at the lowest setting possible, (mine only goes to 170* F) for 10 min, reform, another 10 min, reform, and then let it go for about 30 while keeping an eye on it to ensure it doesn't burn. It should be getting pretty dry by then, then leave it somewhere to fully dry. Luckily it is black so you can rub enough NFO in your hands to coat them, and then rub down the holster to restore a bit of the moisture from wet molding it.
Other than that, I got nuthin'! Good luck and let us know how it turns out