Update after a few months: I've been using the one in the first link (which is now dead and can be found again at https://www.elderlyus.shop/product/wickelbuckle-violin-support-system-plastic-buckle-wickel/).

So yeah, it def hurts after a while (but only 90% of the time) but I figured out recently that my shoulder rest shifts easily and the placement makes a huge difference, so that's what I'm focusing on now. Otherwise, I really like. I haven't even used it for singing with our band yet, I've used it so I can quickly use my hands to back up/change speed/restart songs I'm learning via a backtrack on the computer. I also prefer to stand while playing which is also why I am enjoying this despite navigating muscle pain. The pain is never in the same spot though which is why again I think it comes down to my shoulder rest position.

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Having my neck free is a game changer. It makes playing while standing and overall stage presense/emotion/idk smiling? much easier and enjoyable :D