Here is a nice item if you are collecting US WW2, a rifle waterproof cover. 
Used for Normandy landing on June, 6th 1944, these covers were crucial to the success of the invasion. What a soldier will do with a jammed rifle ? 
One was issued to each first waves soldier. It can be seen on lots of pictures and movies (saving private Ryan for example). You can typically insert any type of rifles, M1 Garand, M1 Carbine, BAR, M1919 and Springfield for example. 
These items are in unissued condition dated January 1944 and made for the Normandy Landing. They seem dark as multiple layers are overlaid but don't worry they are transparent. 
Found in Normandy in 2001.