--- Stillman & Birn Archival Sketchbooks "Delta Series" - These come in both hardbound or spiral-bound binding. Excellent paper.
--- Strathmore Hardbound "500 Series" Mixed Media Art Journal - 90 lb mixed media paper. Review here
On the other hand, if you want exactly the paper you want (or are used to) and exactly the size you want, you can have your own sketchbook bound at FedEx Kinkos. Make a stack of papers to the size you need, cut two heavy board covers to fit, and take the stack to FedEx and ask for "coil binding"