Ted,
If you are unable to find these, one suggestion would be to take a section of strap steel (you can buy this at Tractor Supply or Lowes). They should carry a long section of steel that is really close to the width of those nuts. Just mark out where all of your cuts and holes will be and be sure to allow for the width of the blade for the material you'll lose when cutting. I'd start with drilling and tapping your ten holes first and then use a metal saw and cut them apart. You might need to hold the parts with a pair of pliers and hit them with a grinder of sanding belt if you want to put that taper on the sides.
Best of luck,
Chris