I don't have a G4 but a G3, close enough I guess...
I use this one. Allready lost the cap, but now with the short Spektrum antenna that stays under the body it wouldn't be a problem. Put one of those Traxxas standard rubber caps on.
"Der Schweighofer" in Austria ships to all States within Europe for 6€ shipping costs.
This is the place where I got mine.
I don't know any Danish rc shops, but every shop that offers robitronic products should be able to get this mount as they are the distributors in parts of Europe.
Have you tried one of your local shops and just asked them if they have some sort of antenna mount for you?