The interior mirror for the 407 and 408 was mounted on the speaker surround you are seeking was a Winguard MA.1233 was a dash mounted one similar to the Jaguar XK140, maybe the same.
These are obtainable from
www.holden.co.uk part number 090.103 £46.79 each including VAT.
Brian Morrelli at Bristol Cars may be able to assist on the overhead speaker surround of Brian May.
I suspect that all this applies to the 409 as well.