I don’t have a 3D printer, but I have a wood shop, so I carved a mount for my analog adapter board + TBS Fusion to clip onto my Walksnail Goggles X strap. Works well so far!
It would have been easier to drill the holes for the side where the cords plug in before cutting out the interior. I ended up finishing the profile with a jigsaw, just going very slowly to avoid splitting off the side.
I used a scrap left over from turning a piece of birch.
You mention it not working with the A/V out of any VRX. I’m sorry if you’ve already considered it but I wonder if it has to do with framerates. Madstech videos on the goggles x showed that video in/out only worked when the goggles x display was set to run at the same framerate as the external device. I’ve run into this when trying to output to a tv that only supported 60FPS. I usually fly at 100FPS and had to turn it down for the output to work.
I was also frustrated by the lack of DVR for the goggles. I picked up a runcam dvr and am going to attempt to integrate it into my module setup. I’ll report back with details if I can get it working. https://shop.runcam.com/runcam-mini-fpv-dvr/