The pen-shaped "PIT VISIBLE BLUE" is the best to use for pasting on a small surface area. The tip width is 7.5 mm. It indicates blue color at the beginning to make sure you apply it on the right area. After 3 seconds, it comes clear color which won't impact the appearace of your work. The body of the glue pen is slimer than a regular glue stick. It is very convenient for you to keep it in your pencil case.
The glue pen is refillable with Tombow Pit Visible Blue Glue Pen Refill - Pack of 2.