Hi, was reading up on how to make a c&c cage and found the information below:
Seville Classics
Even though this company is the distributor to CostCo and Sam's Club, they do not directly sell the full boxes of grids, other than as an accessory--9 grids for $10. However, if you really need extra connectors, this is the place to get them--a pack of 10 for $5 plus shipping. They do have a retail store locator for CostCo and Sam's Club.
Hope this helps!
Also, Rober May of Holloway Limited sells connectors.