Exclusives like these are usually done when a distributor contracts for a certain number of handguns and can then specify unique features, in this case a 5" barrel and unfluted cylinder. Exclusive means the product won't be listed on the S&W web site. The number required for this special run is typically 2500 or 5000 units.
Check with Bud's but I suspect you'll have to look for a used one or find a dealer that still has a few left. A few other dealers did have this product.