but no luck so far -
I just glanced through my MSC catalog (where I've been getting some of my milling machine stuff, it's an industrial supply place sort of like Graingers, but w/ a slightly different mix) and have found the opposite extreme - how about a 10HP, 240/460V, 3Ph blower that puts out 21,120 CFM?
Think that will give you enough volume?
Or if you want a blowhole, they have a 7.5HP, 3Ph, unit that gives 47,000 CFM (free air rating)
On a more serious note, they do have a section for 'Blower wheels' ranging from 3 25/32" D X 1 7/8" W to 10.75"D x 10.5" W. CW and CCW rotation. You'd have to come up with your own motor and housing, etc. but that isn't as hard as the blower.
The only other alternative I could suggest would be checking out the various auto salvage yards and seeing if you could find a car that used something of appropriate size. I would think with sizes from mini-imports to SUV's you might be able to come up with something that would work.
Another place that MIGHT have something is either an RV / camping trailer store, or possibly a boat supply catalog (ie Boats U.S.) Those are the main places I can think of that would use 12VDC blowers as opposed to AC stuff.
Gooserider