I always keep some spare cables around the house like this
Just for testing. Fish around Ebay or Newegg and pick up $20 of various cables for testing. A $10 multimeter would tell you if that PSU molex were active. It likely is and you have a bad fan.
Here is a nice quiet Scythe 120mm Slipstream
that will fit your case. Comes with an adapter so you can plug it in anywhere you want.