This was a quick and dirty design. I've included the OpenSCAD source, which was quick and dirty, but I figure it's better to give you the source than not. I flipped it over for printing on my ultimaker 2.
I love to make things and teach people to make. You can often find me at libraries leading workshops and making a mess!I'm also a team member of wyolum.com and make Open Source Hardware, such as the Raspberry Pi Alamode