Found a pack of 12 Mini Gel Pens from Staples for $4 and hoped it would fit my pen holder from Silhouette. I was disappointed to see the pen won’t go into the holder all the way. The Pentel Metallic Gel Roller fits though!
I took Staples and Silhouette pens apart and realized the Staples pen length was longer, but other than that it was about the same as Silhouette’s pens. So I stuck the cap on top and taped the whole thing to prevent it from moving. After my Silhouette pens run out, perhaps I’ll just cut down the Staples length and that will be my instant refill.
Here are the comparisons of all 3. Just click on the thumbnails to see a good enlargement of the details.