Ubercart: how to block users from purchasing non-shippable products.

Hello.

The drupal install is using ubercart. :)

I have a client who wants myself and my team-mate to find a way to block customers from purchasing non-shippable items in a similar way the Out of Stock Notifier module does.

Essentially the client now wants products to have "two categories". First category, being items that can be shipped where this module would function as it does now. Second, items that can't be shipped where it would block user from adding the product to the shopping cart, and instead of saying "out of stock" when stock hits zero it would say "Call Now to Order and Arrange
Pick Up (1.866.KAYAKS6)" no matter what the stock levels are.

Is there an easy way to do this?

The only solution I can think of is modifying the "Out of stock Notification" module because it already blocks users from purchasing, it's just making the rest of the modifications for the rest of the behaviours based on an existing CCK field on the product.

I'm looking for other options.

Site: http://ottawapaddleshack.ca/shop_dev
Module: http://drupal.org/project/uc_out_of_stock