Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2122851.
Inspired by MontagueFlange's http://www.thingiverse.com/thing:2118083 , for the longest time thinking about how to design a simple but elegant toilet paper holder, I finally made this.
Just cut a piece of 1/2 inch PVC pipe to length to hold the roll.
Since there is only one screw, stick a double sided tape to the back of the brackets to prevent them from twisting when mounted. Install as shown in the picture.