Chicken Stock alternatives?
Rule number one with sauces: don't miss an opportunity to add some flavor. The worst thing you can make is a bland sauce, and while I doubt a little water or watery store-bought broth would bland this one up, I'd use whiskey myself. It's liquid, the flavor should be compatible, and I've never seen a college student who couldn't lay his hands on a bottle.

Bullion cubes/granules are fine, but, again, I'd probably add booze instead of water to hydrate them.