http://www.vibco.com/    I have two 12 volt vibrators for knocking fertilizer out of trailers from Vibco.  They are about 10 years old.  One is fine, the other one, due to operator error,  is unreliable.  I did not tighten it up correctly and it slid into a large shaft and damaged a brush holder.   I should send the damaged one back to Vibco to be repaired, but we rarely need more than one.  Vibco makes hundreds of different vibrators, You can call them and they will recommend one for your application.