I love the design of damm301 http://www.thingiverse.com/thing:73489
But I need one for the kids with some more tubes.
It is by far not so artfully because I am just an engineer - though I hope you like it :-)

There are two files.
penholderhollow.stl
This is made for printing without infill. But they may be problems to get the perimeters tight. That did happen to me because I didn't want to print so long. Though I printed slowly it took 8 hours.
penholder infill.stl
This one needs Infill and will close the gaps. The bases of foots have support inside.

Edit: 5.3.2014
"œpaeonius" suggested to make the middle section thicker.
So I added:
penholder_hollow_armed.stl
penholder_infill_armed.st
And a (not tested!) repair cone, that hopefully you don'™t need ;-)
repair_cone.stl