After trying a lot, I came up with a way to use my white and metallic gel pens on the explore. It is a very homemade fix, but I bet soon enough somebody is going to make an adapter.
So here it is.
I used a Pilot Choose 0.7 white gel pen. This is the one I found fits all the way into the adapter that comes with your machine.
Remove the Cap
Push it all the way into the pen adapter (there is no need to take the adapter out of the machine, I did it just to take the picture)
You will notice the pen is a little bit loose in the upper part, so just shove a couple of pieces of paper on opposite sides to make it stay in place and the tip doesn't move while writing.
I realized I could use this case with other brand refills, so the pilot pen works as an adapter really.
This is the Background and you can download the SVG of course. It takes a while to upload and about 15 minutes to finish.
Support AWESOME SVGs
Pilot white Gel pen