Play.com in the UK are selling the official Sony ACS-5220E charger for the PRS505 at £15.99 including free delivery (as compared to Sony retail of £24.99 - damn the old 1:1 dollar!).
Yes, I know you can get cheaper chargers, non-CE ones, or even ones for other devices that fit the 505, but if you are interested in the official product here is the link.
PLAY.COM