You don't have to buy one, however ($11 is a good deal though). I made one out of an old door hinge (home style) and a piece of threaded rod.
BTW, don't even think of prying it out with a screwdriver....unless you hate your eyes, teeth, and general complexion. That spring is under more stress than it looks like.
Heed Hood's advice. I did pry my springs out with a screwdriver in my old '91 S10 when I changed my hinge pins. I won't make that mistake again. I guess the gods were smiling down on my that day, since I only took one in the leg and my jeans were thick enough that I only got a bruise.