You could ask a nice butcher to make it for you (mine will provide lamb mince upon request for example) but it is probably more worth your while buying either a mincing attachment for a food processor (if you have one) or using a hand mincer.
Ground/minced beef is easy to find if you go to an actual butcher, not just ALDI/LIDL/Penny (who sometimes stock it too) with Tatar being the steak mince.
Kind of thing you be looking for would be
this.German name for them is a Fleischwolf.
Amazon.de Fleischwolf
Amazon.de Kenwood mincing attachment
Any large kitchenware department, Küstermann, ironmongers will stock them. Fachelmann make the really basic plastic ones (with metal machinery of course) if you won't be using it for that long.
Or try
ebay.
Some also have sausage making attachments (usually the electrical ones).
Just don't try to do it with a normalfood processor - you want mince not slurry.