Whether you're looking for a winger, check cord, leash, bird carrier, beeper collar, e-collar, bumpers, books and videos or other gun dog supplies, the best prices and selection are usually found online at dog-specific sites.
Here are a few of my favorite websites to spend time (and cash) perusing:
Of course, big-box names like Cabela's and Bass Pro Shops have some dog products, but the inventory and selection isn't nearly as complete as these four sites that service hardcore dog-training needs:
*Dogs Afield: A massive clearance area of items marked up to 50% off. Has gear grouped by use, such as launchers/wingers, collars, books, clothing, blank pistols and travel. Check it out at: http://dogsafield.com/
*Gun Dog Supply: A huge selection of electronic collars grouped by manufacturer. It also has all the training supplies you'd expect, and those you'd hope to find. Owner Steve Snell provides plenty of honest product reviews for you to read, as well. You can find the store by following this link: http://www.gundogsupply.com/
*Gun Dogs Online: I haven't spent near the time on this site that I should. But I can assure you that will change. I like how the navigation of this site is put together: by dog type (retriever, pointer, spaniel) as well as hunting type (waterfowl, upland bird) and even puppies, conservation and shooting sports. What I really like about this site, however, is the large collection of video tips from owner Geoff English and some professional trainers. Check it out here, it's worth your time: http://www.gundogsonline.com/
*Dogwise: A book and DVD online warehouse filled with everything to do with dogs. You can find information on training, behavior, breeding, nutritional/diet and just about any other topic your heart desires. It's a great site and one that I can't visit too often as I can always justify spending money on books! If you need a book or DVD, popular or obscure, start your search here: http://www.dogwise.com/