Wildcat backpack (http://madonion.eu/Plecak_Wildcat_55L_p1419.html), was designed for and is used by JWK (http://en.wikipedia.org/wiki/1st_Special_Commando_Regiment).
If you reenact Polish Special Forces, you may want to check it.
Also, the guy at http://militaria.aksnet.eu/ has pretty decent knowledge and some specialty items (like parachuters' knifes from the 80's), you may want to talk to him.