The dealer is correct - the plastic windscreen scuttle is held on with eight expanding rivets. But I think you are talking about the cover in front of the scuttle.... It covers the e-box, the brake master cylinder and the cabin filter. It's in the parts fiche under air conditioning (not under vehicle trim).
The spring clips are the correct item but the retainer behind them (that the spring clips clip into) are often lost. My dealer lost mine, doing a service, then charged me for new ones. Part number is 51711947419 and it's called a nut.
Read this thread...
https://xoutpost.com/bmw-sav-forums/...ng-loaded.html