Nuk replacement spouts can be hard to find as they are not readily available in many local stores. If they are for sale, many times the companies only keep a few in stock and run out quickly. Your best bet is to try to buy them online.
Stores that we have found them personally in have been:
Walmart in the baby section near the baby bottles and the sippy cups.
Babies R Us carry them sometimes. When we have seen them they have been on the right side of the stores when you walk in, located in the NUK section of the store, right beside the Nuk pacifiers and Nuk sippy cups.
Toys R Us - Every once in a great while, we were able to find them here, but it isn't a place I'd go regularly to look.
There are so many companies now selling them online that it's easier just to shop with the click of a finger. Many people complain about the cost of shipping yet when you really think about it, you are actually saving time and money by having the spouts shipped directly to you.
For those of you who have kids, I'm sure when you go shopping that it's a big ordeal to pack the kids up in the car, especially if it's cold outside. Then you have to drive to the store or stores that you think have the spouts in stock, find a parking space, unload the kids, load them in a shopping cart and then go on a Nuk hunt. Once you find what you need - or, most likely, when you don't find what you need, you unload the kids from the shopping cart, load the kids up in the car, and either go to another store if you weren't successful, or drive home. Gas, Time, Parking, Kid Loading and Unloading. . . hmmm. I don't know about you but I think I'd rather sit at my computer desk, visit Amazon, type in Nuk replacement spouts, click add to cart, order and go have some fun with the kids instead!