I've never been able to find an "economical" source, but a couple of places I know of are:
Green Mountain Soapstone , in New Hampshire, IIRC
Westchester Marble & Granite in Raliegh/Durham NC or ??Scarsdale NY (they sell Brazilian)
There is another company is Schukyl, VA, New World Stone, I think, that bought out the old Albereen stone quarries, which at one time were also owned by the Finnish Co ??Tuli Kivi??, who manufactured beautiful Soapstone Fireplaces.
I'm not sure I would recommend it for a floor, unless you bought it in some sort of rough "Chat Sawn" or otherwise textured surface. As the name implys, it can be a bit slippery.
A poster on another forum asked me to jump over here & see if I could offer you some info. I'm not yet registered here.
If you want, send me an email to irwinstone@erols.com, & I will give you some address's or phone #'s from work after the weekend
David AKA Stoneguy