I’ve been using Seeedstudios Grove system for my Arduino prototyping.
If you don’t know it’s a shield and cable system for Arduino that basically means parts just snap together and you don’t have to mess around with breadboards or soldering. At least for simple applications.
One piece of information I couldn’t find anywhere was how big the mounting holes are on their boards.
After some trial and error today I can tell you that you need m2 (2mm) hardware to suit the holes on the grove sensors and peripherals. The base shield has m3 holes, same as the Arduino.
If you’re in Australia you won’t be able to get m2 screws at Bunnings or Jaycar. I’ve only found them at speciality fastener shops like Tower Fasteners in Marrickville. Google ‘fasteners’ and see if there is another store close to you. (Coventry Fasteners is a reasonably common chain)
If you have the time you can source them from ebay.