Hiding individual product pages

I've got a site which lists both external (affiliate) products and my own and am just setting up Marketpress. In an ideal world, I'd like to have an individual product page for my own designs, but not for anything else. I know the product pages will be created anyway, but I'd like to be able to make them private so customers click straight to the external site.

I can't activate product listings only, as I need the shopping cart etc. (unless I could manually add this functionality and just link to the pages??) The only way I can see of changing this at the moment is by getting rid of the "more details" link on the store pages, but I'm not sure how to do that permanently in a way which will survive through updates.