I cannot find a power cable to fit the phono pre-amp (e.g. Hama art. no.46503). Radio shack tried ALL of their plugs but non fit.
The last time I visited a Radio Shack, it had turned into a cell phone,iPad, Kindle , Nook store and was a shadow of its former self where you could buy electronic parts...so forget them. Find out what kind of plug you need on both ends, how many conductors (wires) and build one for yourself. Very doable even for a novice....not saying you are, buta just in case.
With the limited information provided, your posting suggests that the pre-amp uses a low-voltage AC adapter.
To replace it, you would need to know the voltage and current draw of the pre-amp and the size and polarity of the plug. Some of this information may be supplied next to the power jack on the pre-amp. If you've unsucessfully tried all of the plug tips at Radio Shack, it will be difficult to determine the correct one needed. Perhaps someone who has this pre-amp can help.