[TR] Floppy sun visor

[Dr. Bruce Cairns]

Whilst motoring about with the top down, the passenger-side sun visor on my
'74 TR6 steadfastly refuses to remain in the flipped-up orientation.  I have
replaced the visor and rubber retaining chock, wrapped the end of the visor
rod with gaffer's tape, attached velcro to the visor and the corresponding
surface of the windscreen frame - all to no avail.  I start out my drive with
both visors up and after about 30 seconds, the right side visor is flopping
down.  I need some sort of visor Viagra - any suggestions?
Many thanks,
Bruce Cairns