What I have is 1- 9/16" (40 mm) Brushless 12 VDC Micro fan (Radio Shack). Sounds too small. They made many versions of the Formosa, I think.
Try Radio Shack- see if they have your size.
Let me know what happens. Good luck.
BTW did you have your ballasts die on that yet? I replaced 2 of them on mine.