One of the best ways of providing both shade and a water-proof area to sit on those (very few) wet days is to tile the pergola with the grey/cream tiles which are on most of the roofs.
We stayed at a property on the Resort and they had done the same thing, allowing them to place their dining table and chairs outside, which gave them more room for putting up their sofa bed.
Just a thought..............DB should be able to give you the number of a suitable tradesperson who should be able to do the work for you.
Regards,
Lorraine Braid.