I got this: https://www.amazon.com/gp/product/B072JD3YNT/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

My phone is due to arrive today. I'll update this if it doesn't feel good after. The case is very similar to my 5x case, so I expect it'll be fine. (I have the "Adopted" case for the 5x.)

EDIT: got the phone, put in the SD card and wrapped it in the above case. Feels OK. Not particularly snug, but we'll see. My 5x is real hard to get out of the Adopted case.

I am fond of this one: https://www.amazon.com/Dretal-Resistant-Anti-fingerprint-Full-body-Protective/dp/B072JD3YNT/ref=sr_1_3?s=wireless&ie=UTF8&qid=1532023617&sr=1-3&keywords=spigen+moto+x4+case

+1 from me.

I initially bought the slightly cheaper Dretal but I like the Spigen one a lot more. I like how it feels in your hand, the way it looks, and how responsive the buttons are. Can't really provide any feedback about protection. Haven't had any serious mishaps yet.

Sometimes I like the soft cases. I'm gonna start with this one from Amazon. Looks OK. I still don't have the phone so I don't know how it'll fit. But I'm starting there.

And if that doesn't float my boat I'll probably do the same thing that u/onebigant said and scoop up several cheap cases to see what works.