I have now ordered the OLEDs from three different vendors. Two of three times they had the "right" pinout (the pinout I used for the PCB design). The other time the VCC and GND pins were swapped. On the first picture you can see how I fixed this problem.
The last displays I have ordered, came in these nice cases. I have to build a project which fits in there. (thinking of an ATtiny and a coin cell, ...)