How can I adapt my pedals to account for a difference in leg length? I have a leg length difference of as much as 1cm due to a non-biking accident.  Adding padding to my shoe doesn't help. A friend recommended that I get pedal stacks (and a longer bolt) to my SPD-style pedals (or any other clipless pedal) for my shorter leg. I know it will affect the rotation, but it's better than wobbling on my bike with uneven hips because of the 1cm difference. Any advice? And where can I buy a pedal stack or any other equipment, so that my leg muscles are as even as possible?
Be very careful about making leg length adjustments on your bike. There are several red flags about this. All of which you may be aware of or may not. 1st, a leg length difference is very difficult to diagnose, ecept with an experienced physio, or an X-Ray/MRI. 

Most good physios will send you for an X-ray if they suspect a leg length difference is causing you an issue. 2nd, The body will naturally compensate for up to a 2cm leg length difference with pelvic tilt, and while that is less helpful on the bike, you don't automatically need to add stack height if you have a leg length difference.

And last, a 1cm difference in length does not mean a 1cm compensation, even if you do need to compensate. It is something that needs to be looked at professionally, and any compensation needs to be worked in slowly. Generally, adjustments in the 2mm range in one go are considered appropriate. More than that can(not always, but quite often) cause bigger issues than they solve. 

Long story short, be careful what you do, go see a professional medical bike fitter, preferably a physio with extensive bike fitting experience, and follow their instructions. Oh, and be prepared to pay for the privilege, while realizing that it will take time to sort you out properly. There is no magic bullet fix here.

Look up the Boulder Center for Sports Medicine. They specialize in issues of exactly this type, and they designed most of the equipment to diagnose and correct them. Like the 3D bike fitting camera systems.