I went to xcart and they did a little customisation for me that works a treat. I think they charged me U$50
In the area where you add/modify a product under Availability I got them to add an option called.
Visible, but not available for sale.
This then allows you to show the product in a Coming Soon category and it shows no buttons.
Here is my daughter's site with it working.
http://www.thatsmekidz.com.au/home.php?cat=7
Cheers
Chris