Firstly welcome rrenner.
It might be an idea to make a template of your roof.
Take the template to a junk yard and try out the template against other car/truck roofs that might match the crown of your own,cut out what you need and go for it.
Personally I would prefer the repair to be in metal rather than fibreglass.
The other option as you say is a glass sunroof,the problem there is room for the slide mechanism,bearing in mind most sliding roofs retract into a void behind,there's not a lot of room in a TF roof,unless it's the lift out style sunroof glass.
