You're missing the spring/tab thingy that engages the slots in the bottom of the star pediment that you have.
It is essentially a curved piece of flat spring steel that has a keyhole slot in it that the bottom of the pediment drops through, the you slide it over to one side, locking in the star pediment.
I am looking at some junker 114s, will see if I can snag one for you. I just took the star off a 108 going to be junked, but I think I tossed the spring thingy.
You'll see it here, below the #54, but it is greyed out, so might be an NLA part, or only available with the other bits...
SLS | 88 Chromteile Frontmaske