You asked:
You Where can I find this bracket?
If you can find a part number just do a on-line search and if it's listed a NLA or discontinued, go to Flea bay and search the part number and if nothing surfaces that you want to pay for do a SAVED SEARCH WITH A PART NUMBER AND ONE WILL USUALLY EVENTUALLY SURFACE AND YOU WILL GET A EMAIL NOTICE of such. Those anti rotation rods are hardened steel not just soft steel. (and sometimes will make you drop a jaw for a new replacement's price, but are protecting a pricy part)
Take quite a bit of piddling around to use the pipe method.
If the electric PTO is not being used I've seen where a Bubba and Rube Goldberg sometimes instead of replacing a broken or missing anti rotation bracket and they only wanted to use the tractor with no deck and the PTO was not needed as you mention they (RUBE and Bubba) would disconnect the wiring plug to the electric PTO and then take steel wire and tie the 3 corners of the PTO clutch bracket to the frame so the PTO bracket would not friction rotate so as to just use only the motion drive pulley.
Redneck engineering.