There's an utility called bcp to extract particluar pieces of boost (http://www.boost.org/doc/libs/1_38_0/tools/bcp/bcp.html).
boost-root-dir$ bcp filesystem /destination_directory
will copy all the dependencies you need.

I won't give you any answer, it's just my blah-blah:
I had a similar problem when I wanted to use boost program options -- the guys I was working with told me that it's just rediculous to pull such a load of code that exceeds or own code base by an order of magnitude. My point here that couple of dozens megs of boost code in your repository does not harm anyone. Okay, it's big, but who cares? So what? We now have plenty of space -- the space is not a problem per se -- our perception is the problem. What is the real show stoppage here, except someone's dim unconscious feelings? Anyway I was never persuasive enough -- they forced me to reinvent the wheel and do stuff by our own hands.

So in your case, like Konstantin Litvinenko (I suspect) tried to point out, there is no reason to stop yourself from using boost::filesystem.

Regards,
Anton Daneyko