There is the "email only" gateway which would work with an offline credit card solution (eg. receiving the credit card details over the phone). Google Checkout should work for Canadian merchants.

The latest version of eCommerce Express also has a modular structure for payment gateways so 3rd party developers can make their own gateways which work with our cart without touching any of our code. So if you have a developer, we do have doco on how to create a new gateway:
http://c5extras.com/add-ons/ecommerce-express/...
(see under "advanced tips")

We also offer custom coding services so if you have a particular gateway in mind, I can provide a quote for integrating that.

JB