EWilliam,
Check out Jeffs Outfitters at jeffsoutfitters.com. He has a Sharps repro rear sight that is a very good copy of an original for about $75. It'll give you a good idea of what they looked like if you want to try to make your own. You might also get one from Shiloh, don't know what they would charge. Dixie Gun Works probably has one also. What was the problem with the tang sight that caused you to replace it? I might be interested if you don't want it.
Best