It's held in the Natural History Museum in Vienna; here are some photos

The type specimen for the Hyacinthine Macaw is held in the Natural History Museum in Vienna. It was acquired by its representative in an auction of the Leverian museum collection held in London in 1806. You can read about it here as well as view images of the type specimen and the plate in Shaw's famous work. I am grateful to Nicole Ludwig from Cologne again for sending me photos of the type specimen after she visited the museum in Vienna recently.