In reply to Le Sapeur:
I note you said 'emergency', so I presume it's to carry in case the dog is injured?
I've idly pondered it, and a lot depends on the size and weight of the dog.
I have a 30kg Lurcher, and I run him in a webmaster harness, purely because he has a really high prey drive, and if he escaped it could get messy.
I can lift him with the haul loop, but due to his weight I don't think it would be particularly comfortable for the hound for any length of time.
As well as the dog, you have to consider yourself. In my case 30kg isn't light, so assuming I have him in a comfy harness, then what? You then need to somehow attach the dog to yourself in such a way that you could carry him over possibly rough terrain for some distance. Any light collapsible carry harness is going to cut into you quite badly.
Best I can come up with is that for something like an injured leg it should be possible to support the dog while it limps out. I carry a couple of climbing slings that, together with my Canicross lead and belt, can be lashed together to support, but not carry for any distance, the dog in his harness. For serious injuries it would be like a small human casualty, it would probably involve a bunch of mates or even MRT at some point.
You could try looking at the various harnesses available for walking disabled dogs, one of those could be suitable as a 'just in case'.