Use Wolfcraft mini clamps (part number 3455100) or any other similar to clamp your Bosch or Mafell guide rail.

You can still mount the original bracket to the other end of the clamp so you can still use it for inner clamping of things, see my second photo.

This is no rock solid solution as the original clamps, but you wont have to use much pressure for clamping, it's just for fixing the guide rail position

100% infill recommended, use PLA or PETG