If you have a large mason contractor nearby, you might want to see if you can buy some leftover
brick from them. It's a small chimney, you may be able to get a high quality brick and even a
custom mortar as well. Take a picture of the flashing before tear down and remember that
cricket!
https://=image+of+a+chimney+cricket&iax=1&ia=images
Yah it would seem to me the cricket and flashing will be one of the most important pieces. I plan to take a bunch of pics along the way and hopefully run the details by y'all here to make sure I'm on the correct path.