That's an intriguing idea, Hans! Like Beth I don't know anything about this Tunisian parure (is it known how Queen Fabiola acquired it?), and I haven't found any significant examples from Tunisia, but regarding ethnically influenced jewellery we can always rely on Lalla Salma and Morocco isn't too far away:
The designs of Lalla Salma's belt and Queen Mathilde's bracelet have certain similarities and the size of the bracelet would surely match the centre part of a belt. I'm still not sure if the designs of the earrings and the bracelet are indeed similar enough to think of a suite, but as I said, it's an intriguing idea!