Failing any of the above, it is not terribly difficult to get a top up card in Canada. I am heading to the GTA in two weeks and I usually stop at a local 7-11 where I am going and get a Rogers voucher there. I then dial *868, enter the voucher number and I am good to go. I too wish I could top up over the Internet with a US credit card but it is not possible. Unfortunately the vouchers expire so buying one and stashing it for future use is not much help.
I support the right to keep and arm bears.