Brackets can be cut from a length of 2x2" 1/8" walled seamed square tube. This is considerably less tedious than beating your own from flat stock around a former, though somewhat less accurate. Select from the available cutoffs at your steel dealer to find lengths with minimal bowing in of the sides. Cut the brackets to size (it's best to cut each side one at a time rather than through in a single cut to achieve a square shape). Drill 1/64th undersize, then use a hand reamer to finish the hole. Finally, cut off the side with the seam, cut off the sharp corners as triangles, then finish rounding the corners on a bench grinder. I used a bristol board template to transfer the appropriate shape. Once cut, the bracket will spring inward slightly, but this will be corrected when you tack in place, as the bush tubes will force the brackets back into shape. Use grade 8 bolts long enough so that only the shank portion contacts the brackets. Cut off excess thread and use a good quality lock nut to secure during final assembly.
For my shocks, I used the same method to make the brackets, however the location of the bolt holes must be adjusted to allow the shocks to move freely.