For a wartime 35mm I second the Kodak 35, from what I recall Kodak made a miltary version is olive drap or black, I have seen a few that were modified for use with parascopes. But the Speed was the most common camera in use, at the end of the war the Combat Speed was issued and were used as late as Vietman.
In small quantities Leicas and Rolleiflexes were stated to be used, bought off the shelves or 2nd hand. Though not modified and though not the standard cameras these two, as the two above, were put into type-related, designated camera kits.
Also private owned cameras were used by photographers when they considered them superior to the standard one. (Zeiss Super Ikonta B above the standard Speed Graphic)
The US Govt. bought some Leicas during WWII through intermediaries in Switzerland and South America. They were shipped through Vichy France and the Iberian peninsula to South, then North America. Leitz Canada is a post war creation. E Leitz New York is a wartime creation. Kodak Ektar lenses can be dated by the first two letter in the serial number. EC is 1941 EA 42, EM 43, EE 44, ER 45.