I got my Variax port working! Since I wanted to make it work so badly, I went on with the NE8FDV-YK I bought earlier. I did not manage to find anything better in Europe.

The NE8FDV-YK has a complately different PCB than what's in the Variax 500 guitar originally. Luckily I found a guy with proper skill and equipment who was able to remove the PCB from the old connector, and solder it together with the new connerctor. Most of the pins and holes are compatible and fit nicely.  On the other hand, what I discovered to be a nuisance, the front side of the NE8FDV is a little bit different from the original Neutrik connector which was in the guitar. The RJ45 connector is just a plain RJ45, no issue there, and also the round inner part where you connect the fortified Variax cable is fine. But the mounting holes do not fit exactly in the original panel, so I had to drill new ones into the connector, very carefully. I'd even say it's good and firm enough.

Conclusion? With some effort and skill (and a spare Neutrik connector) you can fix this yourself. My Variax connection works now! Of course, your warranty is void in case you tinker with your guitar like this. But if my warranty was still valid, why would I attempt to fix this myself in the first place.

Also, I found this (http://www.fullcompass.com/product/406186.html) but I was a little reluctant to try it, as it looks differently from what I have in my Variax 500 guitar. Someone else might find it usable though.

Well if you don't mind opening your guitar and taking a look, you should see for yourself. Maybe post a picture if unsure.

What I really liked about the "guts" of the variax guitar was that everything was so neatly modular, theoretically you should be able to replace many ports/connectors without soldering. A pity I could not really make use of this in my case, as I could not get hold of the appropriate replacement part.