Two SIM cards

I believe the only iPhone 13 models, that support two physical SIM cards, were designed to work in China mainland, Hong Kong, and Macao. As such, it would have to purchased in either one of those countries or the online Apple Store that supports those countries.

Ref: Using Dual SIM with two nano-SIM cards - Apple Support (HK)

The iPhone 13 Pro Max is discontinued and no longer sold by Apple.

The only place to buy any iphones that support 2 physical SIM cards is China, Hong Kong, or Macau.