Links to notebooks that I have tried and can recommend.
Weather-proof reporters notebook.
Write in the rain. Great way to take notes in the rain, on a boat, or in a sweaty gymnasium or practice hall.
Ampad reporters notebook.
Excellent, but I find the 8-inch notebook a bit awkward for carrying in a pants pocket.
Moleskine 5.3 x 3.5 inch pocket notebook
The classic. Expensive, but they work. The one that I use.
About the same size as a US passport. Soft covers, easy to carry with you everywhere. Good quality writing paper.