These are made by Bathsheba. You can buy it on her site, at: www.bathsheba.com.
Klein bottle is a exotic math surface that has only one side. That is, a ant crawling on the surface can get to the other side without crossing any edge. (the natural space of Klein bottle is 4th dimension. In 3-dimension, as in the picture, the ant would have to pass wall. For more about Klein bottle and a app for interactive rotation, see: Klein Bottle.)
Note: Bathsheba has also been creativen in Second Life.