There's the Grin Tech Bottle Bob that uses a hose clamp, or Lekkie in New Zealand make a CNC machined mount that California Ebike is ordering in and should be available through their store website in a few weeks. However as others have said it's not enough to rely on to hold a battery upside down, EM3EV for example do not recommend mounting upside down their batteries that use the Hailong battery cradle.