Where can I buy an IPhone with two Sim Cards in the US??

You cannot, unless you buy a used phone originally sold in mainland China, Hong Kong or Macao. Those are the only places where new iPhones with dual physical nanoSIM slots are sold.

Everywhere else in the world, current iPhones sole have a single nanoSIM and a single programmable eSIM.

Using Dual SIM with an eSIM - Apple Support