Fleischmanns makes an unsalted margarine that's also lactose-free (the reason why I buy it for DH ). It's right next to the regular Fleishmanns, with a gold and green label.
Tillamook makes unsalted butter... but that may only be available in the PNW. But our unsalted butter is just with the regular butter; not in the frozen stuff. I've never heard of it needing to be frozen... interesting.