I literally faced this problem on my last build. I second KC Studly's suggest to make friends with a fab shop or roofing contractor- basically anyone with a sheet metal brake. I couldn't find anyone who stocked extruded aluminum angle in angles other than 90 degrees. Not without a hefty set-up fee, anyway.
I wound up actually kerf cutting 2-inch strips of 0.063-inch diamond plate aluminum and using my impromptu homemade brake to bend the strips to the correct angle. But you can beat diamond plate with a mallet and it still looks brand new; can't do that with other aluminum. So, again, the brake wins

You could use small rubber washers under the truss head screws to help with waterproofing.