Sorry for the late reply since you probably already have your pH adjusters by now. But I wanted to research it before I posted anything (and still haven't had time). But realistically I think you would be better off not using anything to try to raise the pH until you can get to the hydro store. You said it would only be a day or two, and anything you add to the
nutrient solution could affect the
nutrients. So in the long run I think your plants would be better off just waiting until you can use a hydro pH adjuster, rather than using household products.