Is there a universal USB adapter that you could connect? The original one seems to be no longer available....

I just had the same problem and since my headset was no longer under warranty and unfortunately I only found USB receivers for the G933 and other few headsets on Logitevh's spare parts list, I was forced to get a new one. I now play with the G933, which can also be used without a USB receiver. I hope for your sake that yours is still under warranty, then you can contact either Digitec or Logitech yourself.
Many greetings