Yes the 256-21645-01-00 could be used, but its a XS 2 part.
I have a late XS1B with the 256-21645-00-00 version. According to the parts list it should be the old version on the XS1 B but I saw a lot of XS1 B's whith the newer version.
The diference between the early (00) and late (01) version...