Assuming you have factory wheels just get some vice grips and latch on to the nut as tight as you can and try to turn it off that way, at least that's what I would try.
As far as a harder nut, you could find one I'm sure but at the end of the day I much rather have a softer nut and strip it rather than stripping the axle threads out. Your wheel nut needs to be tight but there's no need to hang on it, next time just put a little loctight on it 🙂