We need a proper tactile experience and maybe LED illumination ?
What matching push button caps/heads do we have?
http://www.digikey.com/product-search/en/switches/tactile-switches/1114206?k=pushbutton
http://www.digikey.com/product-search/en/switches/accessories-caps/1115298?k=pushbutton
Navigation Button Set:
http://www.mec.dk/12-29177-Navimec.php
Knobs:
diamond surface finish looks rather good:
http://www.digikey.com/product-detail/en/KD1250B1%2F4/KD1250B1%2F4-ND/1201657