Try out Puritan's Pride, we use them for vitamins and they always have great deals:
Discount Vitamins & Herbal Supplements from Puritan's Pride
Also, if you aren't already a member of ebates.com, go sign up there (quick and free). When you are logged in there, just hit the down arrow on the drop down box on the left of the screen ("Select a Store"), and in the list of participating websites you will find Puritan's Pride. Just click on it, it will bring you to the Puritan's Pride website and you will get a 5% rebate back from ebates on top of their already good prices.
Before you join Ebates or place an order from Puritan's Pride ..... If you want, I can send you an invite from ebates, and if you order from any of their participating websites (there are a couple hundred or more, and I think you have to order within a week of joining), we will each get $5 in our ebates account. You don't have to be invited to join, you can do it yourself and get no bonus, but an extra $5 is always nice.
One point about glucosamine and condroitin, if you haven't already heard ... it does work well, but it takes at least a month before you can tell a difference. Look for good results, but be patient because it isn't immediate. Poor thing, 14 years old is young for arthritis.
Here are the prices at Puritan's Pride:
http://www.puritan.com/glucosamine-c...=0&sortOrder=2
Hope this helps.