You could make that brace with a hacksaw, cordless drill, and files. be quicker with a bandsaw and 20 min on a lathe.
I would never trade that tank for stuff you can make yourself, but that is just me..
I just thought of something, It seems I saw clipons, way back that mounted to the clamp bolt on the outer edge of the top tree, sound easier to make but I am trying to recall how thet stopped from moving up & down.
Could help you out maybe if you tried to make your own..