Well, it's a S775 HSF so any S775 one will do - here are a few examples (height permitting for the last three):
Akasa AK-979SF click here
Akasa AK 955 click here
Xilence XilentBlade LITE click here
CoolerMaster Hyper TX3 click here
Arctic Cooling Freezer 7 Pro click here
For some (or probably all) of the above, the Speeze's backplate will most likely need to be removed. Or removed & replaced with the new HSF's backplate if the latter comes with one.
Can suggest a few more HSFs if required. G