I usually get my sours here, but it isn't a big selection:
Wine & Beer Westpark 9631 West Broad Street, Glen Allen, VA
As far as beer bars go, these are the two to try: Capital Ale have some sours on tap and there are three locations around the area. Sedona Tap House also has a good beer list
Just out of curiosity, which beer are people talking about specifically when they say Jolly Pumpkin? I hear that all the time, but it's a brewery and not a brew.