Well, I know this sounds crazy, but, consider getting another one! Two will keep each other company. It will not only help with the separation anxiety, but the two will keep each other company all their lives, run together, play together, explore together. They are pack animals, after all. I have two golden retrievers, and I have experienced great pleasure in watching this bond manifest itself over the years.
Unless one of the dogs turns out not to like other dogs. I took in a stray like that once. She adored people. If you adopt another one, please introduce them first.