Hey guys, I desperately need your help regarding a tripod I borrowed from a friend. It contains (or contained) an odd top mount that I've never seen before. It's not really a mounting plate, it's more of a little bolt/nut that fits into a hole. Basically, I've lost this bolt/nut and I'm struggling to find how to replace it. I've attached a picture (sans bolt/nut of course). Any help is greatly appreciated!