The vendor I got the couplers from is called Price Pros...I found them to be the lowest priced ($15.20 each) on the Amazon.com website. Retail is over $43 but most vendors sell them for around $18-$22. Here's the link to the Amazon site:
Amazon.com: Prevost (PVOURC061201) Safety Coupler 1/4 in. Truflate Style: Home Improvement