A while ago I remember someone was making the stylus ends that would fit the sierra style (or larger than 7mm pens) does anyone remember which vendor that was?
woodnwhimsies.com has a kit that presses into the end of a pen to convert it to a stylus. Comes in 3 finishes and sells for $2.49. I could not find any information as to what size it was on their web site. You may need to call them for that information. Jim S