I did some research and this is what I found for Setting neutral desert adventures:
https://en.m.wikipedia.org/wiki/Day_of_Al'Akbar Day of Al'Akbar. It's a little more Arabian flavoured then Egyptian/Mesopotamian flavoured however.
https://index.rpg.net/display-entry.phtml?articleid=30671 The Book with No End. This one actually fits well with Desert of Desolation, you are on a Quest for a magic book called the Book with No End that is so powerful it's turned a lush Jungle into a Desert, that would fit as an Imaskari artifact very well.
Lastly Old Empires 2e source book has a bunch of small adventures in it. Plus add in Desert Rules, details about the Old Empires Region and it's culture, Magic, Gods, and History, and current State and you have a very full book at that point, especially if it has one player options/backgrounds and so forth.
Desert of Desolation is over 100 pages by itself, once you figure in quality of life improvements, add 5-10 pages, then add in a Faerunized Book of No End, Desert Rules, and Regional Guide (like W

H and SKT got basically), special monsters and any Player options and you have a full book, no other adventures needed.