You'd probably have to order Orange Triad online, I went through BodyBuilding.com. It has glucosamine chondroiton with MSM in it already, as that is just something like calcium is (I believe it's minerals). So you could buy straight gluco chond at GNC the same way you could buy straight calcium there, or just take Orange Triad which already has it in there the way many supplements contain a bunch of stuff plus calcium.
I've also heard that people like the Super Cissus Rx, and also Animal makes a product called Animal Joint Flex that people like also. Those are the big things people recommend, along with an omega-3 supplement (EPA of about 2-3gm per day).
GLucosamine, but more importantly proper training will help strenghten tendons and making sure you dont have any gross muscle imbalances will also assist you. It doesnt matter how much glucosmine you take if you got a rotator cuff that is weak (or whatever i was just using it as an example)