@Tip and Ring- yes its Home Depot heatshrink encasing neo-mags from K&J magnetics, they sell all sizes and shapes. I don't remember the exact size offhand. I lifted the idea from CPF members Davidt1 and Overclocker, in the ZL mods thread, IIRC.
@lion504- I can post pics this weekend when I'm back home. The pic above is from my phones storage. The disc is just GITD stair tape disc. And, it's a deep carry clip from Mountain Electronics. Less than $1.25 each. I used heatshrink on the clip ends, where it contacts the light. Makes it pretty darn solid, once rotated to a desired position. While I'm sure this is far from the perfect AA, it's currently available. It's ugly, but it really suprised me how practical and versatile this setup is. Easy to remove and use the dedicated headband again too. So, even if you don't like the clip setup you are still left with a pretty durable and affordable headlamp.
I asked a Thrunite rep why this UI isn't available in a " standard " light. His answer was while the headlamp is selling well, there are no requests and/or market demand for it in other models.