I found it at Tuesday Morning as part of a zip-around sketchbook and brush portfolio.
Alas, this Daler-Rowney Classic Watercolour Wirebound Sketchbook seems to have been discontinued. (Probably why it was at Tuesday Morning) It's difficult to find a 140 pound watercolor paper in a sketchbook format, and in this 10" x 7" size. Hopefully they will bring it back or maybe there is a newer version available. If you find something similar, post a comment!