Slide screw mounts onto your automotive relay sockets. Have been made to work with these relay sockets.

There are three versions:

• short (same height as an empty relay socket)
• standard version (same height as relay socket with relay, pictured)
• long (mounting holes above the relay, actually used in my car, last picture).

Or you can make yours to measure by using the OpenSCAD file. Note that it is possible to play with the tolerances in the OpenSCAD to get a tighter or looser fit.