Just confirmed that it is not the OEM battery, but it is a made-in-china Power Source battery. I replaced the 9v in my voltmeter and it seems to work just fine now. The bike battery reads 12.8v until I turn the key to on, then it drops to ~9.8v.
I might go with a Battery Tender lithium (BTL14A240C) for replacement; sepbatteries.com has them for $109.99 with free shipping. Can't find a whole lot of info on them, but the Amazon reviews are decent ($130+ there) and I kinda like the dual terminals.