It is not possible to buy a single colour cartridge separately in stores, and so I tried to order directly from Epson Canada online. At the beginning of the Checkout process it says that shipping is FREE, but later during the process the basic shipping charge is given as $4.95 (NOT free). This is more than 33% of the cartridge price.
When I tried to phone Epson Canada, the automated message said the phone hours are reduced and it is best to email, but did not give the email address, and I could not find an email address online. I am not pleased.