Any button which can make & break a contact, or create an analog voltage, will work with the board (this basically covers
any switch or potentiometer).
If you don't have plans for your digikey voucher in your kit, you can use that to buy a few switches. It is a bit daunting to look through their
switch catalog if you're not sure what you are looking for. Sparkfun has some switches as well and their
switch guide is fairly comprehensive regarding the different types.
All of the materials and part numbers for the switches that we used in the wiki page are included on the page as a
pdf (the 'BOM' under 'Associated Files'). So you can look at the exact buttons we used to make the 3 examples.
They are a little pricey, but our team has been really happy with NKK '
UB Series' switches in the past, and made two control panels with them.