I made my own from some old oak pallets and a band saw. Fortunately, I had the old ones for templates. The front in the two first pictures are the tapered ones, the furthest bolt to the front I used some old cut valve springs for movement. Sorry I don't have pictures for the front as it is masked for paint. The rear is approximately a 2x4 spanning from one side to the other. The center is basically shims, 1 and 1/4" by 4" on each side. I used some thin (1/8") bias ply rubber between wood and metal all around.