I am unaware of an online source for these types of charts.  They must
be updated yearly (in most cases), and as such the government expects us
to pay for them.

They're made by the Canadian Hydrographic Services:
http://www.chs-shc.dfo-mpo.gc.ca/pub/en/

Most fishing, boating and sailing stores in the area will carry the
appropriate maps.  If you're not from the area there are a variety of
on-line stores which carry them.  I like these guys:
http://www.fedpubs.com/charts.htm

The gov does give us free tide tables however:
http://www.waterlevels.gc.ca/english/Canada.shtml

Hope this helps

Bryan