I would think a replacement hose/chuck set would be the usual fix for a broken chuck. It sort of looks like the lever's pivot pin has either broken off at one end or the pin has shifted over so one end is no longer engaged with the chuck body. If the pin isn't broken can it be pushed back in place? Have you contacted Lezyne yet? If they are of no help and if you can't find parts otherwise available look into the Topeak hose kit. I've sold quite a few as a near universal hose/chuck replacements with very good results. The kit has included a variety of optional fittings for different pump/hose connections. Andy