I would tend to gear my efforts to those firms in the areas of high end homes.  Also maybe look in those stock brokerage firms who have a track record of working with high income individuals. Find some agents there who may be helpful.  While social media may be good for many these type of individuals spend very little if any time on social media.  But the high end luxury home real estate agents, those who have properties listed in the $1 million range and up may be good sources because their clients rely on them heavily to find very specific properties!  So check out the top ten to 20 luxury home agents in your market.  Once you do a good job for them they will refer others since they tend to socialize with like kind.  Best Wishes!!