Keeper Collars (martingale and hidden prong collars)
Julius K9 Super Grip Leashes
Redline K9 Sure Grip Dog Leashes
(long lines - purchase a lunge line in the length you desire)
This company also carries dog leashes. We use them to secure our dogs in the backs of our vehicles so they don't jump out when the back end is opened. Make sure the leash is long enough that if the dog does jump out, they won't be hanging from their harness. Always use a harness when securing your dog rather than a collar to avoid choking.
This is the original Educator collar company. It operates using blunt medical grade stimulation (like a physical therapist TENS unit) rather than a sharp shock. Tone and vibration are also available on these collars. Ordering from this site directly ensures that you are getting the latest collar rather than a discontinued model. These collars can also be found on Amazon (just check to be sure it is the latest model). There is a chart midway down the page that compares models. Dogs are able to swim while wearing these collars.
The Leerburg company also sells the mini educator collars
There are 4 videos on this page showing the mini educator being used and explained by various people.