Banana seat brackets are for sale on Amazon. I would get a piece of 1/2" EMT conduit and have an electricain bend it. Cut to size and then flatten the ends for mounting on the axle.
Well measure your seat stays to rear dropout tubes & get bolt on clamps that size, then do the same thing you mentioned with conduit. Whala!!! Then you got the Same thing you posted pic of.
Banana seat brackets are for sale on Amazon. I would get a piece of 1/2" EMT conduit and have an electricain bend it. Cut to size and then flatten the ends for mounting on the axle.