not that i know of, small fan , all small fans make a fair amount of noise when system is under load......
is it making a ton of noise all the time?
is the fan going bad?
( unibodys are usually pretty good about cooling compared to some of the non unibodys i have owned that get quite hot on the bottom)......
I do know of some high quality fans however they are larger 120mm fans for desktop systems, usually HTPC based systems to reduce ambient noise as much as possible. Nexus comes to mind. I haven't spent a lot of time checking out smaller fans since small fans usually turn at high RPM's = a fair mount of noise, so i could be wrong about after market smaller fans........