I don't think there should be a problem, as long as you make sure nothing you use is toxic. I think you can make the paste with flour and water. To make sure it doesn't get moldy or start to disintegrate (for lack of a better word), I think you'd have to seal it...but I'd be cautious about those, too, since they'd probably be toxic. I'm sure with some searching you could find something, though. Good luck, sounds like a neat project.