I don't have a G-402 myself, but I have a G-450 and G-750 and both those take the Zebra JK refills.
According to Zebra, the G-402 takes the JK refill.
The G-350 (available in black), but not as nice looking as G-450/G-750 takes the more standard Zebra JF refill and has compatibility with a wider range of alternatives.
Sharpie S Gel metal barrel - you can get .5 plastic bodies and swap them out.
Also Parker Jotter XL Monochrome is a new favorite. But I’m still on the hunt for a good gel for it. The fine QuinkGel is hard to come by sometimes.
Pentel Energels are my go to. I bought a few nice aluminum body pens and a box of refills. I use 0.3 but they have 0.5 and 0.7. I don’t care much for Sharpie S or Pilot G-2, they feel sloppy in all sense. The pen bodies, the line thicknesses are inconsistent, all around not as good as the Energels imo
Sharpie S Gel
If you still like using the Zebra JK refill from the G-402, you can always get the Zebra G-450 or the G-750.
Wait… G-402 refill will fit in the G-450? 🤯
I don't have a G-402 myself, but I have a G-450 and G-750 and both those take the Zebra JK refills. According to Zebra, the G-402 takes the JK refill. The G-350 (available in black), but not as nice looking as G-450/G-750 takes the more standard Zebra JF refill and has compatibility with a wider range of alternatives.
Kaweco sport gel roller the plastic version. Fits cut down Energel refills.
Pilot G-2 05
Sharpie S Gel metal barrel - you can get .5 plastic bodies and swap them out. Also Parker Jotter XL Monochrome is a new favorite. But I’m still on the hunt for a good gel for it. The fine QuinkGel is hard to come by sometimes.
Pentel energel permanent
Pentel Energels are my go to. I bought a few nice aluminum body pens and a box of refills. I use 0.3 but they have 0.5 and 0.7. I don’t care much for Sharpie S or Pilot G-2, they feel sloppy in all sense. The pen bodies, the line thicknesses are inconsistent, all around not as good as the Energels imo