I made the thermaltake I list above to cool my cable box.
I made a 8 inch fan to cool my mini. the thermaltake version will work for your mini.
I used over size bolts to put it together since I use it to pull the air out of my cable box. look at the thumbnail shots, the first shows the mini stacked on a big silverstone fan with feet and a filter I think it is a 180 mm fan.
the second show the thermaltake 120mm it would work under a mini if I had used shorter bolts . the thermatake will run quiet or loud it has a speed control