In case anyone is interested, we just dropped the Slicci Metallic gel ink pen set:
https://www.massdrop.com/buy/pentel-slicci-metallic-gel-pens
Though they are not nearly as fine as the 0.25 mm size suggested here, they have the same excellent quality as the entire Slicci line from Pentel and they're great if you want a little sparkle on your page.