You could flash with
http://projects.mobileread.com/reade...0%20Update.zip, but it's a modified 505 flasher, so you'll have to flash with 300 firmware afterwards.
Your options are:
porkupan (aka boroda's) flasher:
http://www.the-ebook.org/forum/viewtopic.php?t=12017
amutin's flasher:
http://www.the-ebook.org/forum/viewtopic.php?t=11814
You also might find PRS+ interesting (it adds folder / book history support among other things).
https://www.mobileread.com/forums/showthread.php?t=87914