I do a lot of basing with green stuff (e.g., bricks, flagstones), but you can use pretty much anything. Cork or styrofoam is always good, and common sand and gravels also work. I've also used petrified wood, which can look really cool as cliffs, fallen structural materials, etc. ...

Something like this may help.
http://blog.brushthralls.com/?page_id=3381

I think it could look good even without the purchased items (which I'm assuming might be tough for you to find). Plus, it will look pretty on your shelf until you move. And since you'd be using found materials, if it breaks in transit, you can always fix it cheap!

There's tons of stuff on basing out there. Play around and have fun!