I am not aware of any surviving examples of the costume and it's not clear how widespread they were.

The 17th century copper plate engraving to the right is the most common image we have. It was originally printed in 1921 in Die Karikatur und Satire in der Medizin.

I am skeptical about how consistent the masks were between doctors and regions. They were likely custom, one-off products of roughly the same shape. In the absence of more information, we are forced to make our own creative choices.