Doane Paper makes wonderful pocket-sized notebooks with paper that is fantastically compatible with fountain pens.
I absolutely love my Maruman Mnemosyne notebooks, but they are big and rigid. These 5"x7" Doane Paper pads have similarly awesome paper, and fit in casual clothes pockets, if you need small they also make 3"x5".
The paper is slightly off-white and is quadruled with a light blue. My Levenger, Pilot and Parker's all glide over the paper very smoothly, tho the Pilot Vanishing point definetly shows its "travel-ness" when compared to the Duo-fold. Ink gets absorbed quickly and only slightly bleeds through unless I write with a heavy hand. I tried various Noodlers and Parker Quink black. Noodler's Blue Nose Bear is almost the same color as the grid lines.