Bag of 100 (yes! one hundred!) P100 series 1mm diameter pogo test pins from SEG market second floor. Available in a ton of different head types.
Pin specifications. Download full page view..
Manufacturer's recommended test setup.Download full page view.
Pogo pins are supposed to be used in compatible sockets. Pins have fairly short lifespans. When one breaks you'll be glad you used sockets instead of soldering directly to the pin.