Not exactly what you are asking but here's what I've done. Just put it on any case you like, only 1 store has these here in Greece but I absolutely love them, they are between 3-5€ here.

I've bought multiple and put them on a bunch of cases, matching colours when I can. In my opinion they are more "classy" than Popsockets, allow the phone to be mostly flat and the plastic ones allow for wireless charging even with a "thick" case like the Liquid Air by Spigen.

I've also rocked the Rhinoshield bumper with a blue Momostick on my blue S9+ and it's pretty awesome. My favourite combo is the faux leather Momostick with the Pitaka carbon fibre case.

Keep in mind, there is one that's metal and faux leather, while it looks the best to me, because it's metal it won't allow for wireless charging.

If you are a bit careful and use something like a credit card you can remove it and reuse it, it leaves no residue behind and sticks a bunch of times. Of course on something like the Hyperknit and Alcantara case it won't work.

It saved my phone countless of times from people knocking it over in the bus or accidentally bumping into me, I've never dropped my phone while wearing a Momostick and it even acts like a stand, although for portrait it's not reliable.