Yup, rabies vaccine is something that can wait to make an appointment next day. It’s incubation period is usually a couple of months, or a week in the extreme cases, so a day or two won’t make a significant difference. Not something an ER will triage first.

Go to sleep, call your work first thing in the morning, and make an appointment where they have the vaccine available. I doubt your boss won’t let you take a day to get a rabies vaccine, but if he does, tell him you will bite him if you start showing symptoms at work, ha ha.