I can certainly book TAM flights here in the UK through TAM's UK site: but I don't because domestic flights are inevitably more expensive than those available in BR (and sometimes by a very wide margin). If you have no Canadian site, there might be a default "other international" site. Otherwise you might find flights on the Expedias et al. From the UK these display TAM's gringo fares.

Webjet was certainly accessible, bookable and payable by phone as of last year. But you need deep pockets (or Skype!), a deeper measure of patience and some competence in Brasilian Portuguese.

GOL is (was?) a breeze to book overseas (through its "international" site), but it accepted only Amex.