Well, that will not be an easy task. Depending on a large number of factors, the gun is worth up to $10,000-$20,000. If you do have that kind of money, then good luck finding one. There were only about 2900 made, and many of those were used in the civil war. (which means a lot of those could have been blown to pieces, or ended up rusting in the ground)
My advice? Go find a 1873 Colt Single Action Army. They are more common, and cost less.
Want something easier/cheaper to find? Get a M1895 Nagant Revolver. They are historically significant, have a really cool, and unique design, and can easily be found for under $150 in great condition.