White grape juice would likely work, as would chicken broth (although it wouldn't give you the grapey flavor). I'd make sure that the grape juice doesn't have sugar added, though, otherwise your dish is likely to be a bit sweeter than you're intending. Ginger ale might work, too - I've heard it should work, but haven't ever tried it. I've usually used chicken broth (I get the Swanson broth in resealable boxes) when I didn't have wine in the house, which is hardly ever. These days I get those little four-packs of single serving bottles of wine and keep them around. They're not terribly expensive, and one of those little bottles (like they serve on airplanes) is about a cup of wine.