I believe that the Y straps are original, I've seen the RBN 0/00655/0013 on a P38 holster before, but I can't find who the manufacturer was, using Ades lists:
The Reichsbetriebsnummer RB numbering system.
Water bottle looks OK but could do with better pics of the press studs and markings on the neck and the top.
Thanks for your respond, it seems the y-straps are indeed original but post-war modified for Czechoslovakian army.
For the water bottle I will take a look for the markings!