The first Stars & Crosses campaign expansion: North Africa 1940-43, is on sale at WargameVault. This is a PDF-only rules set that covers aspects of desert warfare, including dust clouds, digging in under fire, flares/night attacks, and hazards to vehicles.
The PDF includes new units (British, German, Italian, and even French!), new terrain types, and four historically-based scenarios to get you started. Buy it here: Stars & Crosses: North Africa