Das strap mod for smaller heads and no parts required I got around the problem of it not tightening up enough for small heads by removing the plastic bits on arms with
Modular Audio Head Strap | Pimax
iNFINITE | Pimax 8KX under the lenses
Pimax 8K VR Headset Offers Impressive 200 Degree FOV, But With A Few Sacrifices - GameSpot