Dairyland Seed is still selling alfalfa seed. From what I see, it is a Corteva brand.

Rob-See-Co sells the WL brand alfalfa.

Chemgro is a PA-based company. They have alfalfa seed listed in their 2024 seed catalog.  I don't know where they source their alfalfa seed from.

Barenbrug sells alfalfa seed.

Alfalfa Partners is a part of S&W Seed Co