1/570 Revell Battleship Scharnhorst

you can use 1/600 scale parts the scale difference is unmeasurable
there are not that many of those either but it will give you a FEW choices

Have you checked White Ensign? This is their 1:600 scale KM Battleship set. They also have KM AA guns and railings.

NIce, thx, I needed that info also!

Thanks for the info. But that set doesn't have railings, does it? Should I get "Ultimate" Kriegsmarine Set 2 Detail Set instead?

The WEM catalog writeup for Kreigmarine Set 1 says ...

1/600 "Ultimate" Kriegsmarine Set 1 - The Battleships. This set contains all the specific parts for the Airfix Bismarck, Tirpitz and Scharnhorst. You only need buy one of these sets to cover all of these kits, plus there are enough parts to build another Scharnhorst kit and convert it to Gneisenau. For each model however, you will need to buy one PE 627, which contains the more generic fittings such as rails.

My bold for emphasis.

PE 627 is Ultimate KM Set 2. To trick out the Scharnhorst with details plus rails you need both. sets. You can model another kit with the leftovers from Set 1, but you need a Set 2 for each ship modeled to have enough railing material.