Where can I buy a hairdryer and flat iron in Oia?
Welcome to the forum.
You might struggle to find those things in Oia to be honest, you’d be better off going to Fira, the main town.
You will definitely struggle to find any electrical appliances in Oia but for these things you can always ask your hotel or airbnb as they usually offer these things for free obviously.
If that’s not an option ten definitely a visit at Fira will solve your problem… any large super market like “Sklavenitis” should have these basic appliances.