I've stripped the pieces off Onager's old battery and will drop it by the hazmat station next time I take syringes in. After I split it and identify the component batteries, I think, so that next time I /can/ just buy the components and do it myself, without being paranoid about it.
edit: ah HA! Paranoia pays off. These are 12v 20Ah batteries. All the ones I was finding at vetco and alphatronics were < 8Ah