I am a licensed esthetician in NYC and interested in becoming a
distributor of Sisley cosmetics. I have tried to contact Sisley
through their website but was unsucessful. Can you tell me how I would
find the distributor that handles Sisley in NYC? I am intersted in
setting up an account with them. Thank you for your help.

There must be a cosmetic trade association that provide details. Try
them as starting point.

Try this link to trade associations. They are bound to have a book
with distributors in

http://www.cfsan.fda.gov/~dms/cos-trad.html