This is my simple (crude) pen holder fabricated from stuff just sitting around the shop. The body is 1/2" plastic pipe with a hole drilled in the cap on one end. To make the pen ride centered in the tube I slid over two plastic bushings. These are the roller inside the case of the sample floss the dentist gives you. Not only centers the pen but serves as a stop to prevent it from falling out the hole. After inserting the pen with bushings I added two foam ear plugs to act as the spring. The top cap then holds it all in place and is not glued just a friction fit.