Berlingo Towing mirrors

ClubMember11B8C4C51B

Has anyone with a new Citroen Berlingo got any recommendations for towing mirrors?  I have found it impossible to tighten mine up fully due to the taper on the car mirror surround, and lost one on the way to Norfolk last week despite the supporting strap.
The car mirrors are quite high which rules out some of the makes I have studied in the shops. Any advice greatfully received!