https://jaguar.org.br/

https://procarnivoros.org.br/projeto/projeto-oncas-do-iguacu/

You can write to them

You can search articles which provide accurate information regarding the spps country wise.

Humboldt mention a soldier who fought in Paraguay war and claimed to have seen a white jaguar. This is available in Humboldt's big book.

Leandro Silveira once told me that a old guy in the brazilian Caatinga (northeastern Brazil) told him that, when he was a kid, he saw a white jaguar skin in a big shipment of jaguar skins.

Finally, one individual developed white fur (keeping the black spots) in Brasília zoo, deriving from a leukemia.

Recently, in Colombia, a white wild felid was found, see it here it: https://ifmnoticias.com/felina-albina-podra-ser-visitada-por-visitantes-del-parque-de-la-conservacion-en-medellin/

INFO: do you want a completely albinistic specimen or do any partial or leucistic ones also work?

María Cielo Agustina von Fuchs any partial or leucitic works