I think most New Half escorts advertise on backpage and are travelers from Thailand or the Philipines. Appearantly there also some South Asian NH streetwalkers.
Haven't heard of any Japanese independent new halves, only Japanese New Half shops. If there are independents, maybe they can be found in bars in Shinjuku 2chome but thats a wild guess. and i dont think there are many platforms to advertise in Japanese. There are plenty of dating websites where girls discretely negotiate for some pocket money, but they are not commonly used by NH as far as i know.