Protect (expensive!) mattress from toddler "fluids"?

[luv2hike]

Hello! I'm shopping for a non-toxic latex mattress for my 4 yo son. He's moving from a crib to a twin bed. Frequently his nighttime diaper hits capacity and his sheet and puddle pad are quite wet in the morning.

But how to protect a new latex mattress from pee, the stomach flu, etc.??? A high-quality mattress should last him until he leaves for college (latex mattresses last up to 20 years). It's really important that my son sleep on a healthy mattress...but also important to protect that mattress!

A wool pad under a cotton pad is one idea. But that's 2 more things to buy on top of an already long list (mattress, foundation, sheets, pillow, etc.) and I need to control costs.

Any other thoughts?

TIA,

Deborah

Edited by luv2hike - 8/15/11 at 4:11pm

[luv2hike]

Found an option...http://www.naturepedic.com/products/pads/organicmattresspads.php. Organic cotton surrounding a polyethylene-type waterproof layer. Not as natural as pure wool or cotton, but completely waterproof. And certified non-toxic by third party GreenGuard.