700VDC is tough because it's not an industry standard voltage. 500VDC, 600VDC, then 1000VDC are standards. Many devices are rated for 600VDC, but very very few are rated for 1000VDC, which is what you would have to use.
It's going to be VERY expensive too. What do you have that is using 700VDC, and where is it coming from? Generally on something like this, since the source is usually a rectifier fed by AC, it's easier/ cheaper / safer to disconnect the AC side.
If this is a solar PV application, I think that ABB and a French company called Socomec have 1000VDC rated solar PV disconnect devices. They are typically multi-pole devices and you run the DC through 2 or 3 poles in series to get the necessary air gap required to interrupt a DC arc.
I use Gigavac contactors for general EV stuff, and I have read their spec sheets that list voltages above 700VDC. All of their stuff appears to be single pole single throw. The largest of the Gigavacs claims load-break in the >1000A range.