Anthony, I agree that a GND filter is often not the best tool, and digital approaches offer a lot more flexibility. I've never done it myself (yet), but I've seen some impressive results with manual blending of two exposures, one taken for the sky and the other for the foreground, perhaps along with some dodging and burning. It's more involved than turning the job over to an HDR software program, but it might be worth checking out for scenes like this where you want to preserve those brilliant sunset colors. I have a friend in Australia who took a photo trip with Hans Strand, and manual blending received a lot of emphasis; he's sold on that approach.
I essentially have two different camera systems with common filter sizes but only one set of filters. I know the feeling when you're out in the field and realize the filter you need is at home in the other bag. This has happened so many times that I'm going to get a second set of the key filters, probably a 77mm polarizer and a ND filter; the variable ND filters are intriguing.
You're fortunate to have such beautiful places like this to photograph. I hope to see more.