I like the battery cases that Thomas Distributing have. They have 4 AA cases that will also hold 4 AAA, and 2 AA cases that will also hold 3 AAA.
The only 123 battery holders that I know of are made by Arc Flashlight. Their LS will hold one 123, kind of pricey but bright. /ubbthreads/images/graemlins/smile.gif
Kingston sells their SD flash cards in a good case. Some others either don't supply a case, or like Panasonic, they give you a case that's prone to open on it's own. I suppose a piece of duct tape would cure what ails it though.