Try these stores...
Arlington Latin Market (703) 486-0549
La Union Grocery (703) 812-9484
El Chaparral (703) 276-8336. This is the one I go to most of the time and where I have found the soap.
There are also many Latin/Caribbean stores in Silver Spring, Maryland and in Adams Morgan/Mount Pleasant in DC where many Latins and Dominicans live.
The US distributor I gave you is what appears on the package of soap, hummm....very odd. Candado is made by Sociedad Industrial Dominicana C. por A. at Maximo Gomez Ave. No. 182, Sto. Dgo., R.D.
Hope this helps,
Natasha