Hi,

Lilyan.

There are a couple of places you can go to that have what you are looking for.

You'll have to register but its quick and free.

The first one is here -

http://www.ontarget3d.com/site/Products/957-wwii-german-tank-commander-uniform-m3-for-poser.aspx

This is actually a full officers uniform. Its in poser format but once extracted you should be able to find the Geometries folder and pull out the hat as an .obj without any probems. Check out the Texture folder for the image map.

The second is here - 

http://www.turbosquid.com/3d-models/free-hat-3d-model/481619

its a little crumpled looking and needs retexturing for your needs but seems about the right shape.

Hope that helps - let me know how you get on with those.

Maf