I would say this same thing to anyone who's looking for music teacher/tech/tuner/selling, buying, trading instruments: go to local music stores. Almost all music stores I'd been to have public bulletin boards free of use for any music related ads. You can also give your information to them and ask them to refer anyone interested to you (maybe you can offer discounts).
Other options may be:
List yourself (your buisness) in directories/phone books.
Make friends with local music teachers and ask them to refer their students's piano needs to you.
best,
hope this helps.