Forgive any inadvertent noobness - I'm not an arcade guy, but you guys are the Internet-wide experts at buttons

I'm making an electronic musical instrument (accordion), and have a specialized button need:
- Really low activation force - less than 30grams (0.3N), with low/no "click" (auditory or tactile) at the end
- Small - I need button-centre to button-centre to be around 19mm (3/4") or less
- High endurance
- Less than three dollars would be wonderful (I need about a million of them)
Ultimarc's GoldLeafs would be
perfect, if it weren't for them being too large.
The best idea I have right now is getting Sanwa SDM-18's and replacing the springs with something much lighter.
Does anyone have a better idea?