source for decent wingnuts

I have a 1m Gibertini XP on a motor. The dish nuts (ie for elevation setting and fixing the dish to the motor mast stub) are heavy-duty wingnuts, the nuts that fasten the motor to the pole are ordinary nuts. I'd like to replace said pole nuts with wingnuts, but I'm having trouble sourcing some that are of the same heft as the dish nuts. I can find lightweight M8 galvanized wingnuts easily, but they are nowhere near as strong as the nuts that came with the dish.

Ideas? Have tried the usual...

source for decent wingnuts