Think this is rather too late and not really a solution... And the time difference is working against you.... But for anyone else reading this in the same situation:

1) Some embassies will help in a hurry. I had a customer coming from the UK at short notice. I was in Saigon but found a number for trade contact (in London) on google. I rang him from Saigon (where the Foreign Ministry had already closed) and he asked me for a fax confirming the nature of the trip. My customer went in two hours later and they issued the visa on the spot - and even without charge! The embassy was normally closed in afternoons, but they opened the door for him. Believe me, this case was not SO urgent and neither I nor the customer THAT important... but this guy was very helpful. So I would start by searching for all the phone numbers you can find to do with the embassy - eg "trade attache" etc. Obviously tourists will get less sympathy...

2) Most embassies will (=should) issue a visa on the spot if its been approved in VN. My last London experience was 15mins. 30mins is more normal. Same day approval in VN is possible against nothing more than passport details but obviously you need someone in VN to do it for you - so I would google travel agents, law offices etc. You will have to get a payment to them. The firm I've used no longer offer this service to new clients, but for me its always been around US$15 for a 3/4 day service, up to US$50 for same day. This is for a business visa - a tourist visa is much the same - and I've done both. You still pay a fee at the embassy for issuing the visa - which is reduced as approval has already been obtained . In the case of London, the "approval" is put on a database in VN, and a separate fax is sent to them alerting them of it, cc me. I have heard that with this approval it IS possible to enter Vietnam and get the visa put in the passport on arrival - but this must be specified at the time of approval. BUT before even attempting it, I would check with the airline check-in counter that they would allow you to board against a copy of the approval. From time-to-time I've seen travel agents offering "visa on arrival" services. I suppose they are operating a version of this procedure. (Also there are a few countries where visa on arrival is possible without approval - but alas not Australia...)