Here are some options:
French:
* "Comme du pain bénit" - "Like blessed bread" - implies something plentiful and easily obtained.
* "Plein comme un œuf" - "Full like an egg" - emphasizes abundance and being packed in tightly.
Spanish:
* "A dos centavos" - "Two cents" - similar to "a dime a dozen" in meaning.
* "Como la arena del mar" - "Like the sand of the sea" - suggests overwhelming abundance and lack of value.
Italian:
* "Come i funghi" - "Like mushrooms" - emphasizes rapid growth and overpopulation.
* "Un'infinità" - "An infinity" - conveys a vast number and lack of uniqueness.
German:
* "Wie Sand am Meer" - "Like sand at the sea" - similar to the Spanish phrase, emphasizing overwhelming abundance.
* "Ein Dutzend" - "A dozen" - directly translates the English phrase, but doesn't convey the cheapness aspect.
Russian:
* "Как грязи" - "Like dirt" - implies something common and insignificant.
* "На каждом шагу" - "At every step" - emphasizes something being found everywhere.
Ultimately, the best foreign phrase will depend on the specific context and the nuance you want to express.