Sorry to hear that you are having problems with this.
As far as we know there is no restriction on paying by credit card via PayPal in Canada.
To test this, we tried placing an upgrade order, clicked on "Pay with an debit or credit card", changed the country to "Canada" and got the standard credit card form with a "Pay" button at the bottom. It is optional whether you create a PayPal account or not.
If you cannot get this to work, your only alternative is to order by post, details here: http://www.spansoft.org/uk_ord.php