You have 2 options:

1. Scythe Kaze Flex II
2. SXDOOL 120mm Slim Fan 120X12mm

Depending on how many mm you think you need to shave off to make this work. The Scythe fan is 14mm when removing the rubber pads. The SXDOOL is 12mm.

I have used both fans and both are adequate on the IS-55