So you want to mount accessories to the top of your roller shutter.  Offroad Animal offers a universal rail that works with Mountain Top Branded roller shutter with angled top (Not Ford Wildtrak)

There are many M8 threaded holes to mount anything you want. 

Features:

• Full steel rails sit 45mm high 
• Zinc plated and powder coated matte black
• Full hardware kit supplied included square nuts to go into roller shutter T slots
• Works with most roller shutters that have a T nut channel 
• Supplied as a pair

What is included in the box

• LH Rail
• RH Rail
• Square nuts for Channel
• Associated nuts and bolts