If you're not very artistic, I found some templates online for crown designs: This DIY craft would be perfect for topping off a hime kei.
Pink and Gold Birthday Party Princess Crown Favors
Buy Korea Temperament Elegant Queen Silver Crown Clear Crystals Lady Rings at Wish - Shopping Made Fun
DIY Lace Princess Crowns - Perfect for a birthday party!
DIY "Royal Tiara" to Celebrate Barbie Favorites at Toys "R" Us - Homemaking Hacks