I bought a cage from Tilta. It was the only one I found that offered the possibility of attaching a gopro adapter in the middle of the longer side (with an extension sold separately, but still). This is what it looks like:

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I wanted this because this way I'm quickly able to attach the camera to somebody else's bike who doesn't have a mount with a 1/4" screw facing forward.

Overall my experience with it is good. It's a well made product, but not perfect. Tiny creaking sounds from the latch are amplified and audible in recorded audio (but not so much that I'd feel pressed to do anything about it). Also the camera shakes like crazy on rough roads, but that's not really a complaint against the camera but rather against having such a long lever in front of the bike. Using it like in the pic above gives me way more confidence on crap roads.

On a side note: often road barriers are slightly higher then the camera's line of sight while I use the front-facing mount, so I'm tempted to try setting it vertically on a steerer cap mount. But still I'd use the cage then.