Hi Mirek,
It's my understanding that the Dax was a KVA with two inches added just above the side sills to make a taller car. The windshield openning should be the same as KVA, Tornado, GTD, CAV, and a host of other cars.
If the glass won't go then there's a generation loss in the tooling or deliberate distortion introduced by the body manufacturer. Even so anything added to create a "proprietary shape" should only affect the perimeter not the shape of the openning. No worries...
CAV stocks windshields in Canada. I'd bet the freight from Canada to Germany is less than from South Africa, however your best bet is to find something in the EU.
Failing that, I'd be glad to supply you a clear, laminated, safety glass, windshield. Let me know how it goes, Cheers