supposedly this is the thinnest 120mm fan available according to the pdf... http://www.ibselectronics.com/pdf/me/us_toyo_fan/TF120RX_SERIES_AC.pdf it uses AC power though... i'll see what else i can dig up. im at work with nothing to do so i have lots of time on my hands...
It's probably a terrible idea but could you possibly take a file to a fan to get it to 15mm? Sorry if this is a stupid iudea, i'm a complete noob to this modding stuff
This would maybe work for a few mms, but you will see the motor of the fan will get into the way, plus the fan blades are precisely designed so the airflow will probably lower drastically and the noise increase, however you could remove the outer body and leave one side to screw it on and remove all plastic around the blades and stick the fan throung the blowhole outside if this is what you want you want to use it for.
I think Thermaltake might make some thin fans. I posted a link to their site, but I think I'll do a little more research for you to find them. EDIT: I was wrong. This page shows a fan that is 13mm, but clicking on the link shows this page 2 that says the fan is 130mm X 130mm X 25mm.
