I think the problem is not everybody is set up for Visa processing. NicFitNation can do it through AlertPay. But they don't sell nicotine e-juice.
If you DIY, you can try importing plain nicotine juice from China using PayPal, you can get PG and VG from the drug store and you can get flavourings from anywhere. I've got an order into Box Elder (US-based), but I have no experience to make a recommendation.
But, if you can do an Interac e-mail transfer, there are a couple of Canadian vendors that will sell you e-juice. I'm loathe to mention them on the forums lest Health Canada notices them, too. But you've got the list. (I know. If you spend enough time in the forums, they've already been mentioned.)