Hi Steffen
The windscreen can be supplied by anyone who does windscreen glass. It can be cut to suit from flat laminated glass, same as if you needed one for your tractor or boat. I have one in my shed that I could measure if needed, let me know and I can dig it out. Dimensions may be on here somewhere.
If you search “windscreen” in the country buggy section there are old posts on the rubbers.
I think Clark Rubber, Spectrum and others can make them up for you, some will even know what you’re talking about. You’ll need boot, bonnet and windscreen specially made. The piece of foam between the windscreen frame & the body is just a stock piece they’ll be able to sell you off the roll.
Here’s a couple of threads.
http://forums.aussieveedubbers.com/viewtopic.php?tid=80360#pid756970
http://forums.aussieveedubbers.com/viewtopic.php?tid=105012#pid983241
Cheers
Tony