FSDO is an FAA service, and as such is not found in Canada. Transport Canada provides service in Canada very similar to that provided by the FAA in the US.
Depending upon exactly the nature of your enquiry, you should probably start with "Maintenance & Manufacturing" which is the closest equivilent to FSDO
Transport Canada website is very well organized.
www.tc.gc.ca then go to air and then civil aviation.
If you're looking for a specific topic I might have a more precise suggestion...
Pilot DAR