I made some today, it's fairly easy to do and cheap.
I was cleaning out the garage at my parents house and found a foam pad used for gardening, it's to cushion your knees when working on stuff. It was a really dense 1" foam and looked like some of the lifts I had found on ebay. So, I traced the heel of my boots (which I ordered a size too large just for this purpose), and cut out the foam slightly smaller than the tracing as to fit inside the boot. I cut out four pieces using a band saw, two for each shoe and then hot glued two pieces to each other. I then cut them at a sharp angle. They fit in perfectly and raised me about two inches, not including the sole of the boot. Very comfortable, and like I said cheap...since the foam didn't cost me a dime.