Do I have this right, or do I exaggerate? In any event, several products fit the bill. The Integral Designs Siltarp ($55) is really just thata tarp. You'll need to figure out how to mount it on hiking poles or tied to trees. It's a useful thing to have, but my guess is that on a dark and rainy night, with those tracking hounds baying in the distance, it's not something you want to fiddle with.
In any event, single-wall or double-wall doesn't matter a whole lot. Single-walls are typically very expensivemost Bibler tents, for instance, are $450 and up. I'd suggest you just get a small double-wall tent. A great choice is the Sierra Designs Clip Flashlight ($189), which for various reasons has come up often of late. It's a very compact two-person tent that sets up quickly and is extremely weather-resistant. And it's lightless than four pounds. Another good option is L.L. Bean's little Microlight ($119), a tent that's similar in design to the Flashlight (two-pole, hoop-style) but designed for one person. Weighs about the same. A third good choice is Mountain Hardwear's Tri-Light, another solo tent, which also weighs in at sub-4 pounds. Alas, it's also pretty expensive at $275. But a good little tent.