Dont know about Midlothian...There used to be one at Waxahachi but that was dropped a few years ago..James Kemp who has now passed away was one of the major promoters at Waxahachi.
I dont know anymore who has a list of ALL artifacts shows in a year. At the front desk at the shows, flyers are usually available for other events. The main ones at this time are Temple, Fredericksburg & Luling. Google for details.