in reply to Getting statistics from an attached device (printer)

(Repost due to DB hiccups, twice)

Scraping the GUI using WWW::Mechanize is likely the easiest path, especially as you've already looked at the stuff that gets sent using the Live HTTP Headers.

Alternatively, I'd sniff the whole network traffic using Wireshark and see what SNMP packets get sent, and if any of these belong to the HP namespace.