Talk to your boss to see if he'll help out a little bit. Half-half or something. If he's a pretty cool dude he might go for it but it is kinda a big thing to ask the day before you go. If not, just do the second part of what I said.

:p

Just be all "Sir, I'm kinda strapped for cash do to the move but I was wondering if you could maybe go half with me on a lunch party for everyone in the office."