Check w ww.dixiegun.com for hammer pairs. You will not find an exactly matching hammer. If you want them matching, you will have to use a pair of replacements.
There are those who would recommend never shooting any damascus barrelled gun. I am not one of these; you will have to make your own decision. There are guns I will shoot, and there are ones I would not. Bonehill was a respectable maker, and that looks like a nice gun. Measure the length of the chambers, they may not be 2 3/4". The proof marks on the underside of the barrels and on the water table of the receiver should tell you useful information.