Margaret - been diagnosed with skin cancer on my face. Need advice with SPF sun caps/hats

I have recently been diagnosed with skin cancer on areas of my face. I am using topical chemo cream for 4 weeks. Begun to get very red.

My question is over SPF sun caps/hats. Something I’ve never worn. I searched online and ordered a wide brimmed cap but even when adjusted was too big. 

Return is so expensive so want to get more help and advice with what I’m choosing. Never been a hat person! But know I must now.

Thanks