There is a small cigar shop in downtown Gettysburg. I doubt you can smoke in a bar in PA but there may be some with outdoor patios that will allow smoking.
The Dobbin House is an excellent place to eat, they may allow cigars at the bar, I can't recall. Heres a list of outdoor dining venues:
http://www.destinationgettysburg.com/places-to-eat/outdoor-dining.asp
The Fairfield Inn, on that list has a outdoor porch. I think that I recall folks smoking there (food is also excellent).
Cigars International is really excellent, if you are traveling via I-78 (its a fair clip from Gettysburg).
Have fun!