Free Vallisneria Americana
Upstream, in healthier parts of the Hudson, lush forests of vallisneria americana grow. Disturbing these plants would be an environmental tragedy, but fortunately for you there's no need! These plants regularly get uprooted by weather events and destructive human activity, and you can find them washed up along the shores of the entire Hudson River, even NYC. Look for coves and beaches where the river's flow is slowed down: you should be able to spot washed up val leaves. If you look carefully, you will find specimens with roots still on them.
Make sure you quarantine for an extended period before introducing to your tank!