Two things that are problematic -- the first is fairly easy to solve, the second not so.
First thing you have to make sure is that the output voltage and amperage is correct. Your laptop should have a sticker on the bottom indicating what that is (the powerbrick will have that info for sure, but that doesn't help much now

). The laptop should be able to handle a very small amount of variance, but that's at your own risk. Too much and it could cause damage or fire.
What's harder is finding one that has the right connector. Radio Shack used to make a 'universal AC adapter' that came with selectable output and a collection of plugs. It would still be kinda hit or miss.
If you really need it, a real one is probably your best bet, although (based on my experiences) you're odds of finding the right one at Best Buy are pretty slim unless it's a fairly new laptop.
For four days, I'd just suck it up and enjoy a small break from the modern world