Professor wrote me a recommendation; I need another one with short notice but he hasn't replied About a month ago I asked a professor for a letter of recommendation with 2 weeks notice, he agreed and wrote it. I found out about another opportunity but the deadline is tomorrow; I sent him an email Tuesday night asking if he could write me a letter of recommendation again but he hasn't replied. Could he possibly not be willing to write me another recommendation? 

He doesn't have office hours until tomorrow at 2:00 which seems really late to be bringing it up to him. But, I don't want to bother him by sending him another email in case he's ignoring my request on purpose.
Speaking as a professor who writes a few dozen letters of recommendation a month (it seems like that, anyways), I would suggest that he is not ignoring you; he might be behind on his e-mail or simply preoccupied with other matters. 

I would recommend sending another polite follow-up e-mail, and barring that, drop by his office hours. 

Usually, the first letter of recommendation is the most work. Sending a second one is a lot easier, as your professor should hopefully just be able to make a few minor alterations and send it off to this opportunity.