Check out this compeltely useless 2D pen that lets you spend a lot of time just making the thing. Of course, if you never succeed in making the 2D pen into a 3D one, you might have to take more time to re-assemble it until you get it right.
Just go buy a regular pen but this DIY 2D pen is a cool concept. For traveling, you might be able to stick a piece of this 2-D pen for slimmer travel.
Innovative and unique, the Falter 2D pen makes you work for your ink. The “assembly kit” comes with a flat piece of iron that you fold into a 3-dimensional pen holder. The assembly kit includes a key to help you bend the metal, a ruler and instructions. Handmade in Italy.