What is the link to a specific Content-Type Galley?

My idea is to open a lightbox to the multimedia content-type when the reader clicks on the cover image for the article. The media is a remote URL hosted someplace else, but I couldn’t figure out how to create a custom link to that remote URL. I think this will help reduce the amount of clicking it requires to go and back to the article. I did notice that all galleys are assigned a unique ID no matter the content type. And if there is a remote URL, the link to the galley is what the OJS assigns, and after that it redirects. Any ideas?