HP posts the MIB's online, but they are a little tricky to find if you do not know where to look.
To find the MIB archive for HP Laserjet products:
1. Navigate to http://h20147.www2.hp.com/sppmain/
2. Click the link for Appliance Printing Development Kit
3. Click the link for APDK Developer Kits
4. Change the Kit Area drop down box to LaserJet and Digital Sender
5. Navigate to LaserJet and Digital Sender > Printer Management > Printer Specific MIB's
6. Search through the posted MIB files and review the contents
If your specific printer model is not posted under one of these directories then find a similar model and use that one instead. Most of the time the MIB's do not change very drastically from one generate of printer to another so if your in the ball park with a similar printer you will be fine.
Enjoy!