The two best I know of and use are the Silver Puppy ($99) and the Silvergen SG6($199). Both have auto shutoff when a certain ppm is reached. The Silvergen has a control to vary ppm and a mechanical stirer. The Silver Puppy shuts off at 20ppm and has no controls and stirs using a small bulb that sits under the production glass. Both will work great and produce excellent CS. You can get cheaper units that come with three 9v batteries but the Silvergen and Silverpuppy are the best AC powered no fuss generators you can buy.
Blessings
Steve