Pentel EnerGel Alloy broken push button replacement

The push button of my Pentel EnerGel Alloy (RT BL407S-A) snapped off someday, and I lost it somewhere in my school when it was in my pocket.

I found that the caps from Pilot G2 ink refills with the open end chopped off near the taper works pretty well. So I designed a placement push button for it with some measurements from the G2 refill cap