Stadium Truck turnbuckles will be far too long, plus Associated parts will be imperial threads and fitting so the ball cups won't fit your metric balls and also the metric Ansmann ballcups won't thread on the turnbuckles.
Go see A1 Hobbies, they have a load of Ansmann parts in so might be some on the shelf, if not they'll look after you or Lewis may have something kicking around in the workshop that will do the job.