I put an awning slide on rail/track setup on my old van between the rain gutter and pop top. If you've seen an awning on a pop up camper you'll know what I mean. The rail can be purchased anywhere. My idea was stealth because the pop top covered the rail when top was down and I stored the awning in it's bag up in the pop top (big CCV top though)
Pop up camper awning was cheap and so was the rail, about $300 total.
There are lots of ideas like this out there that will be cheaper and simpler than these newer overpriced awnings but please, please don't drill holes in your rain gutter. I think you will regret this, especially if you live in the rust belt or near the ocean. Try to fab up some clamps instead.