About Andrew said... some brave? ;)
What about attaching an SSD to the 5D Mark III?
There is actually a way to connect an SSD drive to the 5D Mark IIIâ€™s card slot, but it is currently untested. The adapter in question is the Sycard CF Extend 165. This goes from the CF card slot on your camera to a PCIExpress interface with ExpressCard slot on the end. However as it is a very niche hardware developerâ€™s tool, Iâ€™m having a hard time finding one in Europe.
Various options exist for ExpressCard slots. There are ExpressCard SSDs like this one which top out around 256GB, though whether it will be any faster than the best CF cards remains to be seen. Thereâ€™s also the question of power draw and whether the CF card slot can provide enough power to the SSD.
You can even attach the super fast 2.5â€³ SSDs for PCs and Macs to the ExpressCard slot via an E-Sata adapter and caddy, though I very much doubt the CF card slot on the 5D Mark III can power it all. Youâ€™d very likely need an external power source for that and a E-Sata adapter that would allow you to connect one.