A German language version of the instrument should have been established and validated, as we plan to use it in a validation study of another instrument. The measure should be suitable for the use with adolescents (12-17 years).
Thanks a lot for your input! Yet, finding a German, adolescent-friendly version of any of those instruments is a difficult task.
I thought about using the German version of the Attachment Style Questionnaire (ASQ). In other countries, the ASQ has been applied to adolescents already. However, the German version has only been used scarcely .
Another option would be the German version of the Relationship scales questionnaire (RSQ, the review you attached also mentions it), which has been used more extensively. However, it includes some questions about romantic partners which is why I am hesitant to apply it with our younger respondents.
Look up Greenberg's Inventory of Parent and Peer Attachment.
If you are looking for a categorical measure, you can easily adapt Bartholomew's forced choice four-category attachment measure. I don't recommend using it as a single measure though, since it lacks temporal stability. You would be better off using it as an add-on to a more extensive measure.
Another possibility is to use select sections of Pottharst's Attachment History Questionnaire.