Freebie extension

I need a following extension: When someone buys a certain product, they receive an option to choose to download one out of several files as a gift.
Does anyone know if such an extension exists? I searched through the market place, but couldn't find one...

May this helps you , please check below url if it can fulfill your requirements -

https://www.opencart.com/index.php?rout ... n_id=30910

Thank