Sorry to hear about your little Tobie. We bought another yorkie puppy for our Sophie to play with when Sophie was 8 months old. Her name is Hazel and she was 7 months old at the time. We made the mistake of getting a second female close to the same age and it didn't work out so well and due to aggression issues toward Sophie we needed to re-home Hazel after a couple of months. It was very sad because we became attached to her but our first responsibility was to Sophie's safety and happiness. Hazel now is with friends in a good home so that worked out well for Hazel in the end but my advice would be not to get another yorkie of the same age and sex. It's just my opinion but it was also the advice I received her on YT from some here in the know.
Jackie & my
Sophie 