Unfortunately, at the present only car seats meeting the Canadian or United States motor vehicle safety standards are accepted for use on board Canadian aircraft. The CARES harness is also accepted and so that might be an option for you to consider.

A description of what is acceptable in Canada, including the labelling that is required, may be found in the following advisory circular:

Transport Canada Advisory Circular 605-003 - Child Restraint Systems

The only other option might be to request an exemption but that would cost $475... so it's not a very good option.