Cutting and grinding tools - either a hacksaw, file and sandpaper, or a rotary tool with appropriate bits.
Safety gear - you will need goggles if you're using a rotary tool on the pen, be careful around hot-glue, and read the safety instructions on the packet if you are using epoxy. For the safety equipment needed when you use it, check the video in step four.
A large syringe. I acquired mine from school, but you can sometimes get them from pharmacists - ask for large oral syringes.