I bought this one from Amazon for car mount also acts as Qi charger. It comes with O-ring so that it doesn't interfere with coil in the middle. O-ring is used as mounting plate for magnetic mount.
https://www.amazon.com/gp/product/B074149XPS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
This looks promising. I hope it has enough magnetism to hold a caseless iPhone X. I am going caseless and I don't want to stick a metal plate on my phone.
I tried the mophie charge vent case, and it isn't magnetic enough o support the weight of the iPhone X.
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.