Socket for using old cell phone batteries (3.3V-like) in DIY projects. Customization for different types/sizes of batteries can be done by changing dimension-related parameters in the SCAD file.
Use a caliper rule for measuring your battery dimensions (don't forget to check also both "+" and "-" connectors distance from the battery's left side) and adjust the SCAD file with it (using OpenSCAD, for instance) for rendering a suitable/fitting socket for your unit. Plug a generic-dupont wire (male connectors) on each pin hole and use hot glue for fixing them.
The source code also allows you to enable some support headers on the socket for placing a elastic band and better hold the battery.