i ride in a one k and i love it. they have helmets designed for oval and non-oval heads.
https://www.amazon.com/Defender-Helmet-Large-Black-Matte/dp/B008I1I3KM/ref=sr_1_2?crid=2GLYCYT2LE5ZL&keywords=one+k+helmet&qid=1647454344&sprefix=one+k%2Caps%2C71&sr=8-2
I know that one K has an oval option for their helmets. Not sure on sizing, but here’s the model I have using an Amazon link