Those brackets in the pic above appear to be pentagonal shaped plates with holes drilled for lag bolts to go through. Most metal shops which have a CNC router could make perfect copies, as many as you need. If you have a drill press you can bore the holes yourself and save a few bucks. A 1/8" hardboard template will make sure you get the holes in the same place for each plate. A solid jig that holds the plank square in place to your drill bit will help make the holes through the planks straight and true. You would want to be very careful with this process. Out-of-aligned holes will make for an unstable structure, if you can actually put it together.
The planks look to be 2x6, so the plates would be about 8-10" across and maybe 3/4"- 1" thick. Aluminum, maybe? Steel? Hard to tell.