sources mekorot - Names of mazalot in Judaism

Yesterday we discussed that during Zayin Adar we eat fish due to the constellation of Adar. Rambam lists these mazalot, and uses them extensively when discussing calendar calculations. They are also featured in later piyutim that we say during Pesach and Shemini Atzeret. However, I could only find a reference to the 12 constellations in Berakhot 32b without their names. Do you know any earlier Jewish sources that Rambam could use to create his list?

Answer

I summarise the really good comments that my question received:

Double AA suggested Pirkei deRabbi Eliezer, which is really hard to date, but according to researchers most parts are from late Antiquity, and by the 8th century had more or less its final form. In chapter 6 we read:

כל הכוכבים משרתים לשבעה כוכבים של שעות, ושמן כל"ש צמח"ן: כוכב, לבנה, שבתאי, צדק, מאדים, חמה, נוגה. והם משרתים לשבעה ימי השבוע: יום א' כוכב חמה, יום ב' צדק לבנה, יום ג' נוגה מאדים, יום ד' שבתאי כוכב, יום ה' חמה צדק, יום ו' לבנה נוגה, יום ז' מאדים שבתאי. וכולם משרתים לי"ב מזלות שהן כנגד י"ב חדשים, ואלו הן: טלה, שור, תאומים, סרטן, אריה, בתולה, מאזנים, עקרב, קשת, גדי, דלי, דגים. ואלו שנבראו במעשה בראשית לנהוג את העולם*

All the stars minister to the seven planets, and their names are KaLaSh TzaMChaN (כל"ש צמח"ן): Mercury (כ'), Moon (ל'), Saturn (ש'), Jupiter (צ'), Mars (מ'), Sun (ח'), Venus (נ'). And they minister to the seven days of the week: On the first day Mercury and Sun, on the second day Jupiter and Moon, on the third day Venus and Mars, on the fourth day Saturn and Mercury, on the fifth day Sun and Jupiter, on the sixth day Moon and Venus, on the seventh day Mars and Saturn. And all of them minister to the twelve constellations, which correspond to the twelve months, and they are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces. And they were created during the Creation to drive the world.

Uber Chacham commented that we can read about the mazalot in Rashi's commentary (11th century) to Rosh Hashanah 11b (even though Rambam probably didn't have access to it):

ר"א אומר אותו היום י"ז במרחשון היה יום שמזל כימה עולה ביום גלגל חמה עגול הוא, חציו למעלה מן הקרקע וחציו למטה מן הקרקע, ושנים עשר מזלות קבועין בו וזה סדרן, טלה שור תאומים סרטן אריה בתולה מאזנים עקרב קשת גדי דלי דגים. וסימניך טש"ת סא"ב מע"ק גד"ד, ששה מהן שקועין למטה וששה מהם למעלה

R. Eliezer says: That day was the seventeenth of Marheshvan, a day on which the constellation of Pleiades rises at daybreak, the Sun is round, half of it above the ground and half of it below the ground, and contains twelve permanent constellations, and this is their order: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces. And its mnemonic is TaShaT SaEV MaAK GaDaD (טש"ת סא"ב מע"ק גד"ד), six of them immersed below, six of them above.

_{* Translation recycled from Sefaria}

Yaacov Deane listed many mystical works, like Sefer Yetzirah 5:5 (or 5:2 or 5:4 in other versions), which should have existed by the 3rd century. Sefer Raziel haMalakh contains many parts that were edited in the late antiquity, and at many places refers to the mazalot, here's one complete list.