Strantor, I came across this in the ebay search "400Hz motors". It's a lot less HP than the 8 or so I'd like...
http://www.ebay.com/itm/BRAND-NEW-4...773?pt=LH_DefaultDomain_0&hash=item2edce68635
http://www.ebay.com/itm/BRAND-NEW-4...773?pt=LH_DefaultDomain_0&hash=item2edce68635