Looking for a midrash: B’nai Israel gives Hashem their children at Mt. Sinai

Does anyone know the source of this particular midrash? It goes something like this:

Before the revelation at Sinai, Hashem is prepared to give Israel the Torah, but first tasks Moshe with obtaining from the people their “most valuable possessions” in exchange. After failed attempts to provide Hashem with their precious metals, jewels, etc., Israel eventually offers Hashem their children. This trade, or guarantee, enables the Torah to be given.

All help is appreciated.