There are several good brands to choose from. I went with the Tritronics Sport 60: waterproof, good range, small remote size, durable and because it has a tone in addition to the shock. This way, once your dog is trained, you can simply use the tone most of the time. Their new gen 2 units are smaller and can be turned on by a switch on the collar, a good feature. I had one problem with mine and Tritronics had it back to me in less than a week. The Sport 60 G2 sells for about $260.
My .02. Good luck.
Rest in Peace, Ryder. Boy, you went before your time, in the start of your prime. You were loyal and are missed.
~ 4 March 2013.