I recently dove with two instructors that had a simple GoPro attachment setup:
(SNIP)
One thing I found that I'll try whenever I do a night dive is the GoPro handlebar mount. You can attach any dive flashlight to the go pro and have a budget lighting system.
Have you tried the handlebar mount yet? I saw that setup last year in Hawaii, now that I think about it.
I’m thinking of this (https://shop.gopro.com/mounts/handlebar-seatpost-pole-mount/AGTSM-001.html) on the DGX 600 video light (DGX PUSH Handheld Light Kit - Video Beam | Dive Gear Express®)