Google N-gram Corpus Counts
╭─ーーーーー─┬───────╮
│ 金の小牛　 │   144 │
│ 金の子牛　 │ 1,616 │
│ 金の仔牛　 │    78 │
│ 金の犢　　 │     0 │
├─ーーーーー─┼───────┤
│ 黄金の仔牛 │   510 │
│ 黄金の子牛 │   219 │
╰─ーーーーー─┴───────╯

Compositional and not in the usual refs.

The primary source for Jisho.org entries is JMdict (this project). Sometimes, it will also match entries from an old Wikipedia dump, which is why it says "Wikipedia definition" above that result. (these will not have furigana readings)

https://ja.wikipedia.org/wiki/金の子牛²

From the bible (of course)
The word exists in the dictionary but there is not pronunciation in kanas for it
https://jisho.org/search/ 金の子牛