I am using
this $6 cable with a USB wall charger. It charges all of my devices (ipod, cellphones, nuvi, etc), including PRS-505. Just use the right tip for your device. PRS-505 uses a barrel tip for Sony PSP.
Here is an even more capable model for $3 more.
Makes life a little easier than a plethora of chargers for each device that comes with it's own proprietary plug.