I got some low budget extra pump mounts on line, shipped from asia many years ago. They were generic in sizing. Some of my pumps needed some sleeves of inner tube rubber slid over the cylinder to make the pump fit better in the brackets. And some extra velcro straps to make sure the pump stays where it was put.
Or, if you have a Silca pump, there always is rule 30, no bracket needed:
https://www.velominati.com