Multibanco is one Portuguese payment method that allows the customer to pay by bank reference. This plugin will allow you to generate a payment Reference that the customer can then use to pay for his order on the ATM or Home Banking service. This plugin uses one of the several gateways/services available in Portugal, IfthenPay, and a contract with this company is required. See more at Ifthenpay.
You can find the extension at Chrome Web Store, here.