I wanted to mention that you have not listed all of your options here. When a job is needed today before you consider accepting the consequences of missing the deadline, you might consider paying overtime, hiring a temp [dangereous and probably not going to get it done right], or keeping a virtual assistant on standby and using them.

Generally working with an idividual virtual assistant in business for themselves can be dangereous unless you have some pretty stong references. Working with an agency who matches virtual assistants to clients is a lot better because you get some guarantees and safty net in crisis times.

The costs of virtual assistants can be as low as $16 per hour, but probably a more common cost would be $20 per hour. But you can use only one hour, or two or whatever you need. It is 'on demand'. So you don't have personnel twiddling their thumbs waiting for the next assignment. You just pay as you go.