Maybe a computer shop can help you? I haven't recalled seeing software in shops, but I imagine someone must have it. You could try looking up places and then calling them, perhaps?
Another possibility is the free http://www.openoffice.org/, which is always being updated and can open/save the same kinds of files as Microsoft Office (sorry in advance if you already know this and still need the Microsoft version).
I believe there's no such thing as "cheap MS office suite". When you buy te software you buy the license and it's always the same price. However you can have a nice rebate if you're a student (150 USD instead of 280 USD). If you're not, just find one who will accept giving you his student number or whatever's needed.
Regarding the place to buy it: I'd go for the online process. First you download the free trial version and once it's over (30 days) you buy it, MS will give you an authentification key and you're ok. I advise you to dig the trial version because there are a lot of new stuff in this 2010 version, notably on Excel.
Open Office can be a nice alternative but I never really got used to it (on Mac), and compared to the latest version of MS Office it really looks outdated. It's really obvious when it comes to spreadsheets, Excel is way better.