It looks like a
Waterfield bag. Although it's not the bag in the pic you linked, they sell an "Indy" bag for iPad Mini (called "
The Mini Indy") that would be about paperwhite size. I have their full-size Indy bag that fits 10" iPads.
Waterfield bags are not inexpensive but the build quality is amazing and they stand behind their products. I received a bag with a flaw, emailed the company CEO, and received an upgraded version of the bag as a replacement. (I'm just a happy customer, no other relationship to this company.)