The thing you have to be careful of is that you can't just take a random piece of bar that is a little bigger than the factor bar and bend it to fit. You have to know the physical properties of the bar so you get the spring rate you want. The material, hardening (heat or work hardening), and shape affect the spring rate.
Also, you will probably need to use solid bar, not tubing/pipe.
I'm kinda skeptical about doing this yourself. It might be waaaay more work than it is worth.