Type of Header for Motherboard PWR Switch
This should be a standard 0.1" (2.54 mm) pitched header.

A name of that thing goes along the lines of SIL (single in line) female crimp housing (for the part which goes on the cable) with fitting crimp contacts for the cable.

Something like this and this.



There are certainly some already confectioned cables out there (like in the picture you posted). I'm not so good at finding cables, but I'd go with the keywords: 0.1" 2 pin cable, and see what I'm getting.

Looking around a bit, a good name for a cable seems to be: 2 pin jumper cable

Probably because jumpers are just the same 0.1" pitched header.