Hello
You could try electronics shops as I think they are still used to clean VCR magnetic heads.There are other ones used to clean computer parts ( mainly keyboards) but as far as I know they are made of foam and not of cotton. A solution could be a Radio Shack shop ( I live in France and Tandy shops disappeared long ago, I don't even know if you still have them, but this was the kind of shop I wanted to point anyway)
Now, in the purpose of spot application of paint in modelling world, a much better choice would be microbrushes.