You should try Air transat or Royal, they might help you out as the jump seat is under the front crews responsability. Don't bother with Canada 3000, they are not alowed to take anyone on the jump seat.
By the way, if your company has a interline agreement with Royal or AT you should get a standby ticket then you would get a seat in the cabin or a jump seat for sure unless it's already been given to someone else or the front crew decides other wise.
Good luck.
AL.