The canonical bread flour is France's Type 55, which should be roughly equivalent to German type 550. Both are defined by ash content, with the German measures being 10x the French ones. Now, the King Arthur Flour website lists 11.5% protein content for their equivalent of French Type 55 flour. So, I'm thinking you want a higher-gluten German type 550... which should be obtainable if you can find protein information for your national brands. If I were dead set on matching French T55, I would experiment with adding small amounts of vital wheat gluten to German Type 550 to get equivalent protein content.
American bread flour is slightly different. It is a paler flour with 12-15% protein content. To duplicate the strength of this, you want German flour type 812, possibly with a little type 1050 or Dinkel Mehl 630 added for extra strength. For a less whole-wheat flavor, use type 550 or even type 405 plus vital wheat gluten.
The breakdown on german flour types is:
- American Cake/pastry flour = German type 405, 8-10% gluten
- American All-Purpose flour = German type 550, 9-11% gluten.
- American Bread flour = German type 812, 11-13% gluten. Dinkel Mehl 630 may be in this range too (I find a note that it is commonly used in bread and has a high gluten level)
- American High-gluten flour = German type 1050, 13-14.5% gluten
- Whole wheat flour = type 1600
- Rye flour, type 1150
Frankly, I'd find a bakery that makes a baguette like you want, and ask which brand and type of flour they use for their baguettes. Bakers like to talk about their work, and they'll probably be more than happy to tell you.