is it the Boye set? boyes don't come in a size that makes a 16" needle. Remember, too, that when you are talking about size of needles you are talking about point to point. So if you have a 21" cable and the points you are talking about a 29" circ (the points are about 4 inches each on the Boye sets.)
because their cable is so stiff they just can't do 16"....you would hate knitting with it i think.
Here are some Clover bamboos in 16 inch from Joanns.com. They are on sale and great to work with i think.
That looks like the best that Joann has online right now for 16" in a size 13.
You can look at www.CurrentCodes.com to see if there is a coupon code that will work for you too. I believe their site will still let you use the percent off codes but only on the regular price (so instead of taking 50% off the sale price of $7-ish it would take it off the regular price of $10-ish)
Ebay as usual is a good source for needles too!