I got my Strange Case (new) and "old school" Detroit Locker (used) from Nine Inch Nodular on ebay. Only paid $240 bucks including bearings. I could not be happier. They were really cool about service after the sale.
BTW. That completely assembled unit from JBG is nice, really nice, but setting up the gears in a 9" is "super" easy. You can definitely do it....and save some money. But if you do buy that complete JBG unit you can sell your original as a whole unit and differ some of the cost of the JBG unit.