This is actually a remix, but the source file function isn't working for me, so here's the things I combined to make this:
http://www.thingiverse.com/thing:1097838
http://www.thingiverse.com/thing:30104
This is made to hold the bare Nexus 5X without a case, and it fits onto the common 4-tab or 4-hole GPS/phone car windshield mount.
nexus-5x-case-1d.stl | 46.3KB |