These solutions seem to, kinda, take a stab at the concept, but what we're really after is something way simpler. Think a simple text field into which you type a URL. Then this service would visit, crawl and compile the entire site into a static HTML site (with options to enhance the final version of the static site).

This would have to work independently of the platform used to build the original site and ideally the service would also provide a means of getting the newly created static site onto it's hosting platform (be it Dropbox, Digital Ocean or whatever other platform you want to host the static site).