Most fibreglass structures are made in a mold. The manufacturers will spend a lot of time and money making a mold. Such that they then need to make a lot of the final product to recoop the costs of the mold. It is unlikely then that a company will be able to make a hard top for you unless it has been done already.
There are other methods of making a hard top involving either a one use mold or of using some of the self supporting glass products. The latter likely to take a lot of filling to get a decent finish, the former taking a lot of work to get even a temorary mold smooth.
So in th eend this kind of job is one for the DIY with lots of time to spare. Don't stop asking though. good luck olewill
Dave, you could also look around for a small Co' that makes FG covers for pickup vehicles & 4x4 pickups. (As I've seen in JHB, RSA) They may be willing to make a one-off mould for you. Jeff