On how you have your data, you can probably just add a url property for each instance of the source e.g.:

   {
      name: "original",
      label: "Original",
      placeholder: "Click the button below to generate an original quote.",
      data: [
        {
          quote: "Happiness beckons you once you forget you were looking for it.",
          source: "Eleanor Trent, 'Where's Joy?'",
          url: "link here"
        },
        {
          quote: "Memory is just the past asking for a permanent residence permit.",
          source: "Dr. Selim Farouk, 'The Mind's Archive'",
          url: "another link here"
        },
        {
          quote: "No one knows how Sentience is born, but we sure know how to kill it.",
          source: "Dr. Marcus Webb, 'The Philosophy of Consciousness'",
          url: "link here"
        },
        ...

Then you can access it with .url (quoteEntry.url) and set it as the href of the quoteSourceEl.