We have a couple pair of DB handles that go up to 220 lbs (nearing 300 when using 25lb plates). Had them made in a metal fab shop, though that may not be a option for you. Those threaded DB's tend to wear a bit and become loose for the twist on collars after awhile. Which means that they can not really get tight enought, with the plates shifting when working out. Annoying when trying to lift some serious weight, even could hold a potentional for injury. The hex set screws collars seem to be much more reliable with steady use.
Even those spring lock collars could be better than the original threaded collars. Good Luck.