Roller blinds

We just got new windows put in and need to put our roller blinds back up. The brackets had previously been screwed into the pvc surround of our old windows and the blinds had been made to measure based on that width.Our windows installers advised against drilling into the new windows. The problem is that if I were to attach the brackets into the wall either side of the window, the gap is too big. The blind is too small to fit into both brackets.

Is there a bracket that is in the market that I can use instead ? I don't want to replace the blinds.

Or, is screwing then into the window surround all tht bad?