They're creepy trash plastic zooms of the worst kind, but the Soligor C/D 4.5-5.6/70-210mm Macro MC lens has a 49mm filter thread, therefore I bought the two zooms with a Danubia PL filter (55mm) and a Danubia Circular Polarizer (49mm) for 15 Euro.
Unfortunately it only works at 70mm and Macro position. Only there it can afford a sharp picture in combination with the reverse adapter. Attached to the Canon, the combo looks a little bit like the Yashica Dental Eye.
It isn't really a macro lens with the reverse adapter, but a close-up lens, perfect for portrait shots. Here some pictures: