Actually, the independent bookstores mentioned above do work, but the real trick is talking directly to the authors. It sounds weird but a lot of Latin American writers are active on social media or have their own websites where they sell their books or tell you where to find them. Some have Patreon or Discord communities where they talk about their work. If you follow an author you like, you often find out about others through the connections they have with each other.
The other thing nobody mentioned: check out local literary magazines from your country or other Latin American countries. There are tons of digital magazines and some print ones that publish excerpts from unpublished or recent novels, and that's where you discover people whose full work you then look for. Some universities also have publishing houses with super niche catalogs that you won't see in the normal commercial circuit.
And honestly, if you want something without so much searching, Latin American literature podcasts exist and they give pretty specific recommendations. You're driving or doing something else and suddenly you hear about someone you like. It worked for me more than once - I ended up reading things I never would've found on a bookshelf.