How on earth did I not know about these before!
To quote the Lenbachhaus website: 'Feldmann opened a store in central Düsseldorf in 1975, initially dealing mostly in antique technologies: nautical implements, photography equipment, geodesist’s tools, and vintage toys. In the 1980s, he added collectibles and souvenirs, including many articles that were not available anywhere else. The business did so well that Feldmann withdrew from the art world for a decade to devote all his energy to the shop. After forty years, Feldmann is now closing his store to transform the entire undertaking into a work of art that he has decided to entrust to the Lenbachhaus'.
Apparently the 'Angie Zitronenpresse' was quite the thing amongst German politicians back in 2010 so needless to say (although a little late) I have ordered one for myself. I just hope it will arrive in time for Christmas.