Drake shows 2 hinge mount mirrors for '32's, neither listed for cabriolet. Many people on here can tell you the hinge length on the cars shown, if fitting to yours seems possible evaluate the angles shown and make a guess as to whether they would be useful. Original B or 46 truck mirror stands would be fairly easy to modify for different spans, but I'm guessing that the repros are zinc...?
http://www.bobdrake.com/Categories2.aspx?Id=mirrors1