What do you mean by Postal Envelope?
If you mean the much-beloved and much-mourned eBay/Canada Post co-branded envelopes, they are no more. Nor have they been available for a couple of years.
I bought my last batch of poly envelopes from eBay seller smallautopartsllc which ships to Canada.
Your PO should have prestamped envelopes available at the counter. You can also order them from the Philatelic Fulfillment Centre in Antigonish, although that is mostly used by collectors. These are technically called postal stationery.
If you mean envelopes for ExpressPost or Priority Post, these should also be available at your Post Office, although orders of 10 or more might not be readily available at a Postal Outlet. (Postal Outlets are the one in the drug store or depanneur/candy store. They are privately run and have to buy their supplies from the real post office. Often they keep very small numbers of unusual items in stock since it ties up their capital)
If you do mean ExpressPost or Priority Post, think a bit more about them. They are very very expensive and may not be worth the extra cost.
In any case, most of your product would not fit into them.
For most purposes, printing your shipping label for any service (except Letter) through Paypal is the way to go. You often get a discount between 5% and 25% depending on the service and the shipping invoice number is also your insurance number (except on Light Packet).
