Gunner Dog Kennels
Ruff Land Kennels
Center for Pet Safety (crash tested harnesses, kennels, carriers, etc.)
https://www.centerforpetsafety.org/
Keeper Collars (martingale and hidden prong collars)
https://www.keepercollars.com/
http://leerburg.com/keepercollars.php
Herm Sprenger Prong Collar
Julius K9 Super Grip Leashes
https://www.cleanrun.com/product/julius_k9_super_grip_leashes_3_4in_x_6ft_/index.cfm?ParentCat=174
Educator Collars
This collar 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.
https://www.educatorcollars.com/
The Leerburg company also sells the mini educator collars
http://leerburg.com/electric_educator.htm
There are 4 videos on this page showing the mini educator being used and explained by various people.
http://leerburg.com/ecollars-vs-animal-rights-extremists.htm
Dog Bark Collar
https://www.chewy.com/baskerville-ultra-dog-muzzle-black/dp/117374
Tools for deterring loose dogs on your walks:
Coyote Vest
Pet Convincer