It would help if you said how large a gadget you’re willing to deal with. I have one that I like that is tiny and of decent quality, but spring loaded, so it doesn’t meet your requirements. (It might not accomodate thick phone cases either). One the other hand there are larger ones that can accomodate tablets, but that aren’t so easy to carry around.
Are you ok with the kind where a metal socket is stuck to the back of the phone with adhesive? niteize.com/mobile/steelie