Cosequin is also known as Noractive (we used to have Cosequin here in NZ but it was replaced with Noractive Cat), and it comes in the form of little sachets that you sprinkle on the food. There are 30 sachets in a box, which is quite convenient because you basically buy it monthly. I don't know if it's sold like that in the US, but the manufacturer is a company called Norbrook (they also make Noromox, Noroclav, Norocarp... anyone see a pattern?!!!). This is their website: http://www.norbrook.co.uk/home2.asp
Obviously it would pay to talk to your vet about their products, as they may not have heard of it or stock it. I'm guessing from the Norbrook website, they are UK based.