A while back, I took some beamshots of an EagleEye X6 and a Convoy S2+ triple comparing d-c-fix and a holographic diffusion film from Luminit.
In that same thread, ‘saabluster’ mentioned the layers of diffusion material used inside newer TVs. I haven’t tried any on a flashlight but I’ve had several TVs apart for repair and the material looks promising. It’s also cheap if you keep an eye out for TVs on trash day. 