For that reason, I think that a non-waterproof pair of pants would work well. A few years ago my choice would have been pants made with Activent, Gore's lightweight, water-resistant alternative to Gore-Tex. But Activent can't be had any more. Replacing it, sort of, is Gore Windstopper. You can find Windstopper pants by Concurve (actually, a Gore brand it uses for stealth marketing of its products), and they're available in Europe. U.S. cost is $99, or about 109 Euros.
Sympatex is another popular waterproof-breathable fabric that seems to work well. You might also look for pants made with it, as they tend to be quite light and packable. In this part of the world, a Canadian company called Navarro makes a pant called the Guide Light that employs Sympatex. They're very light and packable. Cost is about $120 in U.S. dollars and there probably are comparable pants from European makers where you live.
You might also find some pants made with Gore PacLite, although that material is becoming scarce as well. It's very light but rather expensive. An example here in the States: L.L. Bean's Ultralight Pants, which sell for $189. PacLite is less durable than full Gore-Tex, but for occasional use the stuff is perfectly fine.
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