I've heard good things about a company called 'The PrinterWorks' for HP (and other Canon) laserprinter parts. They have a web page with an on-line catalog and search facility at:
All kinds of parts are available even down to that little brush stored inside your HP LaserJet Series II: The SX engine parts catalogue shows that the part on page 350 (feeder assembly) as part number RF1-1177-000. It costs $1.23 plus shipping. Or, that 27/21 tooth fuser driver gear (RS1-0287-000). It costs $1.10 in quantities of 1.
(From: Dave Lee (firstname.lastname@example.org).)
I have used them for the last 4-5 years for HP Laser and ink jet parts. They also do some Panasonic parts. Great tech support, good prices, same day shipping, etc. They have treated me very well. Also, service information on a variety of printers.
(From: Paul Strider (email@example.com).)
(From: George Hurley (firstname.lastname@example.org).)
They'll even fax or mail you a diagram of printer subassemblies so you can identify the exact part you need.
(From: Dave Noseworthy (email@example.com).)
(From: SargW1 (firstname.lastname@example.org).)
(From: Sid Ashen-Brenner (email@example.com).)
You may be able to get a Service Sheet with the error codes (among other information). They also sell parts & supplies.