Select interface implementation according to parameter

What is correct way to select interface implementation according to passed parameter?

Let's have following code:

interface PaymentProcessor {
  public function process(Order $order): void;
}

class CardPayment implements PaymentProcessor {}
class BankTransfer implements PaymentProcessor {}

class OrderService {
  public function __construct( // Load payment processors from DI
    private CardPayment $cardPayment,
    private BankTransfer $bankTransfer,
  ) {}

  // This is what is not clear to me
  private function getPaymentProcessor(string $paymentMethod): PaymentProcessor
  {
    return match ($paymentMethod) {
      'card' => $this->cardPayment,
      'bank' => $this->bankTransfer,
    }
  }

  public function payOrder(Order $order): void
  {
    $processor = $this->getPaymentProcessor($order->getPaymentMethod());
    $processor->process($order);
  }
}

What is not clear to me is how can I get PaymentProcessor by payment method name.

I would use code above, probably extracted to some "Factory". But according to answer at PHP - Using Interfaces, Strategy Pattern and Optional Method Parameters I am probably breaking open/close principle. Then what should be correct way?