Here's the rest of what I found.
I was surprised that many editors did not list bilingual texts as a separate category on their website, not even as a search keyword, which made them difficult to find.
[EU] Basque (For Basque-speaking learners)
- Susaeta (Child books):
English
Buy at: Amazon.es
[CA] Catalan (For Catalan-speaking learners)
- AGDE Llibres (Classics, antologies):
English
Buy at: Alibri.es
- Flaneur (Literature, essays):
French, German
- Fragmenta Editorial (Religious texts, also in combination with Spanish):
Arab, Chinese, Hebrew, Latin
- Godall Edicions (Poetry):
English, Galician, Greek
- Susaeta (Child books):
English
Buy at: Amazon.es
[EN] English (For English-speaking learners)
- Bloodaxe (Poetry):
Arabic, Farsi, French, Georgian, Italian, Irish Gaeilge, Somali, Spanish, Swedish, Welsh
- Holiday House (Child books):
Spanish
- House of Anansi (Child books):
Anishinaabemowin, Cree, Inuktitut, Spanish
- Inhabit Books (Books related to Inuit life for children and adults):
Inuit languages
- KidKiddos Books (Child books):
Many languages from Arabic to Ukranian
- Language Lizard (Child books):
About 60 languages, some “smaller” ones, from Albanian to Yoruba
- Lee & Low Books (Poetry for children):
Mainly Spanish
- Lil’ Libros (Child books):
Spanish
- Linguacious (Child books):
19 different languages, some “smaller” ones, from Basque to Yupik
- Mouthfeel Books (Poetry, short stories):
Spanish
- New Directions (Poetry):
Arabic, French, Portuguese, Scotish Gaelic, Spanish
- New York University Press (Academic and classic texts, poetry, religion):
Arabic
- Northwestern University Press (Poetry, stories):
Classical Greek, French, German, Haitian Creole, Russian, Spanish, Vietnamese
- Orca Books (Child books):
Spanish and Native American languages
- Oxford University Press (Classical texts, letters, music, poetry, religious texts):
Classical Chinese, Early English, French, German, Greek (Classical and modern), Latin, Middle English, Spanish
- PIE (Art, Japanese Culture):
Japanese
- Salaam Publishing (a couple of child books):
Several mostly African languages
- Snowflake Books (Child books):
Chinese (simplified and traditional)
- Starbright Books (Child books):
33 languages from Amharic to White Mountain Apache, some “smaller” ones like Native American languages
- Syracuse University Press (Poetry):
Arabic, French, German, Hebrew, Irish Gaeilge, Spanish
- Tuttle Publishing (Child books):
Chinese, Japanese, Korean
- University of Arizona Press (Poetry):
Spanish
- University of New Mexico Press (Mainly child books, local stories and poetry):
Spanish
- Upfly Books (Child books):
Chinese, Japanese, Korean, Tagalog, Vietnamese
- Zephyrpress (Poetry):
Albanian, Chinese, Hebrew, Polish, Russian, Serbian, Turkish
[FR] French (For French-speaking learners)
- Dadoclem (Child books, comics):
Chinese, English, German, Italian Latin, Portuguese, Provençal, Spanish
Buy at: Amazon.fr
- Didier Jeunesse (Child books):
Arabic, English, German, Ukranian
- Editions Bernest (child books):
German
- Gulf Stream Éditeur (Child books):
English
Buy at: Amazon.fr
- Léon Art & Stories (Artistic picture books for children):
English
- Les editions de l’Officine (Child books):
Arabic, English, German, Italian, Portuguese, Spanish
- Orphie (Child books):
Creole, Maori
- Oxalide (Classic stories for young readers, probably simplified):
English
- Skol Vreizh (Mainly child books):
Breton
[ES] Spanish (For Spanish-speaking learners)
- Spanish Bilingual Books (Child books):
English
Buy at: Amazon.es
- Susaeta (Child books):
English
Buy at: Amazon.es
[TR] Turkish (For Turkish-speaking learners)
- Dorlion Yayınları (Classic stories for young readers, probably simplified)
English, French, German, Greek, Italian, Spanish, Russian