Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2867083.
Remixed this remix of a Raspberry Pi Zero USB dongle for GPIO pin access and heatsink. The main addition are two stand-offs for USB headers that I found on AliExpress (10 pcs for ~$3, see diagram). I had to lengthen the design by 3mm to fit this (and left out the camera connector to help sturdy the connector and because I don't have a camera ribbon cable for the Pi Zero). Designed for the Pi Zero W, since the CPU is moved slightly compared to the non-W Zero. OpenSCAD files are included (please excuse the less than elegant edits, I'm not good with computer). I used M2.5x8 screws to secure the Pi and some tiny laptop metric screws for the USB header (M2x3 I think).
4/20/18: Added STL/SCAD files for Raspberry Pi Zero 1.3 (non-W version with camera connector).
These are the USB headers that I used: AliExpress.com Product - 10 pcs USB Male Connectors to DIP Adapter Plate Converter 4 Pin for 2.54mm PCB Board (affiliate link)