The Catalogo de Selos do Brasil volume 1 (I have the 2016 edition, which comes in 2 small volumes) lists postal stationery. Available from the publisher RHM in Brazil, they ship to US/Canada, or at least they did a couple years ago. In Portuguese. Their site is a little confusing to navigate, I just sent them an email and they were quite helpful.
https://www.oselo.com.br//