A roll-top bag with a built-in washboard won’t replace a laundromat, but when you’re living out of a pack, it’s about as close as you’ll get to clean clothes on demand without plugging anything in.

Some people think doing laundry on vacation is a chore, but the reality is you’re either going to wash there or when you get home, so you might as well pack half as much and do it on the road. By ...