Are you guys serious?
You can make that only better to any size you want in 5 mins. Spray with a rattle can satin black. Its dry by the time you drink a coffee.
I cut stuff like that out of a bit of 1.5mm steel sheet. I picked up many such scraps from the nearby college over the years without buying.
If you dont have a vice and hammer to bend it cut it from angle iron...
To cut it out I used to saw it. Now I have my tiny cordless grinder...
To drill the holes, I have my portable drill.
By the time you can start up a computer and search eBay I would have finished it.
Or... Theres many existing cheap brackets existing that may just want some new holes drilling...
https://www.google.com/search?q=Angle+b ... irefox-b-d