I started to make my own cover last winter. Snow got in the way and I haven't had that bloc of time to get back to it.
My rig is different than many. I found 3 manufacturers last year. & posted on them more than once on rv.net. So, advanced search, author as "Little Kopit" forum: "Truck Campers" & may need to go back past 1 year. (Sorry, I'm just home from trip and am saving checking rv.net until I can do a mass of catching up at one go. Once you go in you lose that 'new' marker)
Or also search: "Capt. Caper"
In the U.S. you can probably find a dealer who can sell you the Sunbrella. I ordered my fabric from Capt. Caper. He is very good on advice for dealing with the fabric. You have to have an industrial or semi-industrial machine, plus the sewing and design experience. Custom fits during the construction process are essential.