It might be worth looking on the German ebay site (ebay.de). I have just checked and whilst there are several Kathrein devices listed, none that you are after at the moment. Just keep trying. Good luck with your search. Geoff.
Thanks Geoff for the suggestion , I speak german, german grandchildren Etc, i've had searches running on ebay.de for about 10-11 months.
I kick myself I gave one away and I've seen dozens for sale over the years.
But because they are obsolete (analogue that is) they have disappeared.
I'm sure that one will turn up somewhere. I'll be in Germany hopefully before Christmas I'll be calling in a few dealerships to ask if they have one on a shelf out back I guess.