Are there any local nurseries that have been around for much of the time between that would have been interested in the plants and helped to grow them on for market?

Did they ever export to European growers to access the markets there? Despite the two world wars a number of growers continued over the upheavals, or passed their particular treasures to 'safe hands' so they could restart. Growers in Holland, perhaps, or the Royal Horticultural Society in Britain may be able to give you better leads.

Another place to post could be on the Australian forums as these are outdoor plants for many areas there - and they have long-established horticultural societies. Possibly also South Africa.

Good luck.

Just a quick internet search turns up a wealth of information on Dr. Henry Nehrling and his work hybridizing tropical and sub-tropical plants. Also Meads cultivars can be found.

http://floridagardener.com/gotha/gotha.htm
http://floridagardener.com/gotha/nehrling.htm
http://floridagardener.com/gotha/nehrling2.htm
http://floridagardener.com/gotha/nehrling3.htm

Hope this helps,
Leon