Viking tac switch specs:
Diameter: 6mm (also listed as 6mm x 6mm on most websites)
"Stem Height": 7mm
Body height: 3.5mm
Tactile force: 160gf for grey switches, 260gf for red switches
SPST normally open - momentary
http://www.alps.com/products/WebObjects/catalog.woa/E/PDF/Switch/Tact/SKHH/SKHH.PDF
Ours are about 2mm shorter than the one you listed on Digikey, but some people might prefer the button to stick out farther. If it sticks out too far then you might be able to push "sideways" on it which would push it up against the side of the hole you drilled and actually make it harder to press down. Be sure to look at the drawing in the datasheet before you buy as digikey and mouser are notorious for putting down the wrong dimensions on their product descriptions. Their error rate is low like 1-2% but when you buy as many components as me, the discrepancies cause a lot of problems, so I always check the manufacturer's datasheet.
If you don't want to read datasheets, you can just buy this part from Mouser.com: Mouser# 688-SKHHBW
https://www.mouser.com/Search/ProductDetail.aspx?R=SKHHBWA010virtualkey68800000virtualkey688-SKHHBW