The customer service center at Lake Merritt has BART souvenirs. It is located on the station level of the station. They have windows both inside and outside of the fare control area, however the display case is inside the fare control area. They are only open on weekdays, generally from around 8:30-4:30, however hours do vary. Prices are decent, however are higher for non-employees. Last time I was over there was a few months ago before we moved to LKS from MET. They have t-shirts, mousepads, plush trains, jackets, and other assorted items. It's worth checking out!