Here is something I made that is a lot more convenient that a broomstick. It is made of 1/4" dia HRS, a spring, a short piece of tubing, and a rubber grommet.
I originally wanted to make it so I wouldn’t have to drill any holes, but there was no convenient place in the body, so I did have to drill one hole in the inner fender for the rubber grommet (similar to the early Europa). If putting holes in fiberglass doesn’t bother you, you could make it much simpler by putting another grommet in the bonnet and doing away with the latch mechanism.
To slot the latch tubing, I used a milling machine, but a dremel tool might also work. I welded the small sleeve to the rod, but you could also drill through for a small pin, etc.
This works with no front spring installed, but I wouldn’t trust it in any kind of strong wind.
Tom