here ya go this is where i order all my car detailing stuff and they have good quality microfiber...
http://properautocare.com/micprod1.html
or you can even check a local pepboys or similar large autoparts store they should have them too but of a bit less quality (usually made by turtlewax). these are still good and soft/safe to use just not the pro-grade stuff like in the link above.
just a note if you do buy one or however many (they are great for the car also so i'd get extras) when it's time to clean it, wash it alone not with other materials b/c it will pick up the lint from them...so follow whatever cleaning info it gives you.
-Mike