A group made a Remington 1858 largely out of metal from a Gibeon meteorite (plus some gold, precious gems, and Pietersite).
Information seems to be sparse (I just found that site, and a discussion on Reddit, with a bit of research), but it appears it could be yours for the low, low price of $1.2M. It even comes with six meteorite bullets. It certainly would make an iconic weapon for a character, and could easily have special properties in a supernatural campaign.
EDIT: Turns out this isn't the first firearm made from a Gibeon meteorite - a company called Cabot Guns made what they called the
Big Bang Pistol Set, a pair of matching 1911 pistols made similarly. Personally, I think the revolver looks a lot better (the others have some faked damage to the grips, presumably to help make the weapons look ancient, but I find them a bit tacky; also, the Remington 1858 is a beautiful revolver design to start with, while the M1911 is just kinda... meh). It also costs a lot less - the Big Bang Pistol Set was priced at $4.5 million (almost certainly to match with the 4.5 billion year estimate of the meteorite's age; that's probably also a big part of why they opted for MUH STOPPIN POWAH .45 ACP).