What is needed to get a marker an "F stamp" in Germany?

[Gyroscope]

Someone asked recently on behalf of a friend who is going there for military service. He and his wife play and don't want customs taking their stuff.

 

[Matski]

Any manufacturer that distributes to the country will have one at hand. WDP for example have one at the factory, and I think Smart Parts Europe also have one, amongst a few others.
They should ring the manufacturer/s of their markers and im sure they will point them in the right direction, normally official distributors will have them too