Depending on the style of coupling, you may need to see Pepsi or Coke. I know Leeners sells the actual plastic gaskets and they work great. On my setup I can also use an o-ring. I can't remember the actual size, but IIRC it is one size larger than the post o-rings for a ball lock.
Primary - Apfelwine
Secondary - Niagara white wine
Kegged - AH Special Holiday Ale, AH Cream Ale, AH Honey Wheat
Bottled - Continental Pilsner, Island Mist Mango Citrus, Island Mist Wildberry Shiraz
Up next - AH Foster's clone, Labatt's clone, Hard Apple Cider,
The Independence Street Brew House