Yellow Plunger Tactile Switch, SPST-NO 50 mA @ 24 V dc 3mm
- Manufacturer: Omron
- Product ID: B3F-4055
There are loads of manufacturers of 12mm x 12mm tact switches however AuthentiKit designs are all based around the Omron B3F series, This is the projected type with a small post that sticks up as opposed to ATK205 which is the flat button type. Total height 7.3mm, with lugs at the bottom.
Supplier Links
https://uk.rs-online.com/web/p/tactile-switches/6866777/
Indicative Pricing With Allowance for P&P
RS Online only sell in minimums of 5 but you can get them individually on Amazon/Ebay with free postage.
£1.60
Substitutions
I would stick to Omron. The dimensions and shape need to be exactly the same. Still there are other variants that will work - for example it doesn't matter what the operating force is or whether you go for fancy gold plated options. Here's a link to the manufacturer specs.