If it's a single barrel derringer you want Dixie offers their excellent reproduction Lincoln derringer in kit or finished form. I would stay away from the twist barrels above mentioned, their not derringer size and they also lack something in really first rate quality, I've handled both. There are a couple screw barrel percussion pistols on the market and these are really nice, Cabelas has a nice one in our local store for $100 right now and it's a good value. If you want a Remington style over and under, American Derringer has many to choose from and some of those in the smaller calibers approach the size of the original Remingtons. Davis is even closer to the original size, but their quality is somewhat lacking.