The best options in my opinion are;
Vitaloni Californian (might require some internal reworking on the adjuster ball to get the passenger side angle)
Vitaloni Baby Turbo (what I settled for currently provides easy adjustment and reasonable rear/side view)
Talbot fender style (period correct, not my favorite look though)
All the above options can be found at reasonable prices online or eBay.
FWIW I mounted my mirrors to a triangular piece of Lexan that is then held on with the window screws. No additional drilling in case I decide to change.
Julian