The E5450 is basically a low power 80W version of the 95W Q9650, Xeon X5450. If you're running it in an LGA775 application any LGA775 cooler should work. If you're running it in an LGA771 system you shouldn't need an aftermarket cooler. LGA771 systems tended to have proprietary CPU coolers. You will need to check by brand name of the system, and LGA771 heatsink, not the CPU itself.
Thermalright, and Noctua both made LGA771 brackets to use their aftermarket coolers on LGA771 systems. But good luck finding one.
http://thermalright.com/product/xeon-lga771-btk/