Metalized mylar umbrella? Can you buy one of these? Well, you can, but you have to look hard.
20180813/DuckDuckGo metalized mylar umbrella
20180813/DuckDuckGo space blanket mylar umbrella
20180813/DuckDuckGo mylar umbrella
20180813/DuckDuckGo desert umbrella
20180813/https://www.quora.com/Which-color-of-an-umbrella-is-more-effective-against-sunlight
20180813/https://www.quora.com/unanswered/Why-American-never-hold-an-umbrella-to-block-the-sunlight
This is the article to look to find the info.
20180813/https://francistapon.com/Travels/Advice/10-Reasons-to-Go-Hiking-and-Backpacking-with-an-Umbrella