I bought mine from my local Ford dealer for something in the neighborhood of $10. I actually had my trunk shaved because when you remove the stock emblems, you will have a couple of holes where they mount.
After a while I decided to put one emblem back on the car and stuck on an SVT badge on the trunk. It just attaches via sticky tape. I don't know if the SVT badge that I used is big enough to cover the holes left by the stock badges or not, maybe someone else can chime in with that info...
Kale