I too would suggest Cindy (Chattiesmom) for couplers. I have 2 couplers and have looked many places for them and they are just too big and heavy at most places. Cindy can make them much smaller plus she has a ton of colors to choose from and her prices are great.
I do love how easy it makes things though by using a coupler. You don't have to worry about leashes tangling and the dogs are all in line with each other making it easier for walking.