How can a Canadian citizen obtain a Vietnamese visa while abroad in a country without a Vietnamese embassy?

How can I get a legitimate visa-on-arrival letter or visa for Vietnam? I am Canadian but am in Ecuador, which does not have a Vietnamese embassy. This means that I cannot apply in person. I am also not comfortable mailing my passport internationally.

There are many sites (for example, this one) which claim to charge to obtain the visa-on-arrival letter but after trying several times on 3 different sites, they just do not work. The last step - after they collected all my personal information - dies with an error saying that onepay.vn cannot be reached. I also just realized this might be a phishing scam since the URL ends in govt.vn rather than gov.vn, but I cannot find any site that seems legitimate. Two guidebooks I own do not have any specific info on what to do when you do not have access to an Vietnamese embassy.