what state do u live in? im in atlanta, and we have lots of "classified ads" magazines and newspapers where u can pay like 75$ for an ad that lasts a month. maybe u have something like that in your area.
i know a couple but they local..... best i can think is just get out there normally they hang around with other artist...... at least thats how I met the ones I know
do a city search on Soundclick and look for R&B singers..or goto the the Hip-Hop board in the Soundclick community and post in the Collab section..you will ge some replies..just remeber to post a like to a sample of your work..