I tied a yoke O-ring onto a piece of line and then tied the line to the binding. As far as stowing the pencil, I stuff it into the binding and then take the loop of line and use it as a bookmark. (I often use pop-a-point pencils as well.) I could get a cover, complete with pencil spot, but I haven't felt the need.ClayJar, I also use and like the DuraRite although a drawback is there is no attached pencil and I'm not entirely pleased with how I rigged one.
I just checked the last site from which I'd ordered, and they don't list DuraRite products at all anymore. Strange. (They still carry Rite in the Rain branded products.) I paid $3.90 and $4.55 for the two sizes back when they had them, so the current direct prices aren't at all bad. It's actually cheaper to buy them directly now, judging by my own new searches.I'd also like to know what sources and prices you've found. The pocket spirals on that website were $4.75 for the 3x5 and $5.75 for the 4x6. I googled and didn't find anything less. That's still much cheaper than the other wet notes.
On another note, for underwater gaming, I recently decided to eschew the whole paper-and-pencil route and instead go with grease markers and laminated sheets. The Markal TradesMarker mechanical grease pencil is *excellent*. The only metal part is the spring, and the pencil comes apart easily for rinsing and drying. It's easy to use, even in big blue dry gloves. I'm almost tempted to make a laminated sheet notepad to use with it.