Anoraks are pretty hard to find these days. For those who don't even know what an "anorak" is, it's a jacket or parka with only a half-zip, so you put in on pullover-style. The advantage of such a design is a little more weatherproofing (less of a zipper to leak) and slightly lighter weight (again, less metal zipper). The drawback is that you can't vent the thing quite as well. But for some applications, they're wonderful. I have a dearly beloved seven-year-old Patagonia anorak that I use for downhill skiing. It's fabulous. And, as you note, the zipperless design allows the incorporation of a big kangaroo pocket, which can be extremely useful.
Still, a few makers still manufacture anoraks. Marmot makes an anorak version of its Precip jacket called, not surprisingly, the Precip Anorak. It's $89. And Kokatak makes an anorak designed for kayakers, but it would work great for backpacking. It's the Gore-Tex PacLite Anorak, a bargain at $289.
Best of all may be the MEC Karona Anorak, offered by Mountain Equipment Co-op in Canada. It uses Gore-Tex XCR fabric in a classic anorak design that is perfectly suited for your activities. Best of all, it's currently on sale for $199 Canadianabout $130 U.S. A steal.
Click here for MEC's Karona Anorak.