Tubes cost $5...that's how much it should cost you to fix a flat assuming you didn't cut the sidewall on your tire of course.

I keep a spare bike pump at work and always have a spare tube in my seatpost bag...I should throw an extra tube or two in my desk drawer though. I can change a tube in a matter of minutes with very little mess. Nothing a quick trip to the men's room to wash my hands won't fix anyway.