Through someone's individual entrepreneur from suppliers. Team up with your friends and do a joint purchase once a month. Now there are a lot of official or gray suppliers, everyone has different prices. Google "wholesale hair cosmetics", for example.
What kind of professional cosmetics? I'll write to you now about some "Schwarzkop" and "Vella", and maybe you need something more original. Try estel.m-cosmetica.ru here, they promise the lowest prices. Here's more ilorai.ru