I'm looking for a gp style bonnet if anyone has one gathering dust or wants to swap one for a Manx style that I've bought in error

ill have a dig through the garage might have 2/3

The GP bonnet was originally moulded from a very slightly modified Manx one so are, give or take a gnat's knacker, the same size and fit. What's the problem with it?

I'm looking for a gp style bonnet if anyone has one gathering dust or wants to swap one for a Manx style that I've bought in error

Is it the style you are not happy with or "the fit".     Buggy tubs, bonnets etc , being fibreglas, are forever curing\changing shape and always seem to need a bit of effort to get them to fit. It`s one of those aspects that you have to "manhandle" into a fit that is acceptable. Good luck and all the best for 2020