Using WooCommerce with no price defined

I am wondering how to allow someone to order a product that I have listed in my WooCommerce store that has no price defined. I am using the plugin as an ordering tool for my business but do not want to display the price. However when I leave the price field empty, by default WooCommerce does not show / allow the add to cart button.

The way I am using the system, we just need to be able to take the orders and a custom invoice will be sent to them once we receive and process the order. However they need to be allowed to add the products to the cart and submit the order.

I don’t want to set the price to $0.00 because I do not want to give any sort of impression that the order would be free.

Any thoughts?

Thanks,
~Andy

http://wordpress.org/extend/plugins/woocommerce/