Imagine, if you will, that you are at a children’s theatre performance- a child-friendly version of the retrieval of Mjollnir from the giants. Thor still cross-dresses, but there’s no wholesale slaughter. The children helped create their costumes and the set. It shows, but in the best of ways. (Or so I hope; this is a class/play I’m proposing to teach/direct for my parks and recreation department.)
Thor, Thrym (child friendly version of Þrymr), possibly Loki, and all the male background characters are wearing inauthentic-to-the-max horned helmets, assembled by an adult out of paper products and decorated by each child as they desire.
The “Valkyries” (here more or less the Greek chorus) are wearing similarly constructed and decorated hats with wings on the side, rather than horns. There is probably glitter glue.
So what does Freya wear on her head? Obviously authenticity is not an issue- we’re going with generally accepted visual shorthand. There will be a short lesson on why these helmets aren’t true, but will convey what we need to say and also add visual interest. The hats are primarily a craft project for the children, so Freya can’t go bareheaded.
Most of the images of Freya show her with a bare head, a circlet, or a simple pointed cap. I can do one of the latter two if necessary. But is there anything fancier that you would see and think “Oh, that must be Freya!”? Flowers maybe?