If I lost my HKID and HK birth cert, how can I re-apply it here in Vancouver ?

You need to first apply the birth certificate in HK. It is troublesome to apply by yourself, so applying by entrusting a lawyer in HK is adviced. Detailed imformation is on this website: GovHK: Applying for a Search of Birth Records and a Certified Copy of a Birth Entry.

And the ID card application imformation is on this website: http://www.gov.hk/en/residents/immigration/idcard/

Hope this can help you. Good luck!