Convert posts to products (but keep posts)

Hi,
I have a movie rental site with about 8000 posts – it’s used for as a resource for my rental store customers. Id like now allow customers to now buy the movies as we’re shutting down in the near future.

Is there a way to convert posts to products, but also keep them as posts? I’d like customers to still be able to browse the catalogue, but just allow them to “add to cart” and then proceed with a checkout etc if they want to buy the movies.

Thanks in advance..

The page I need help with: [log in to see the link]