I replaced the knackered rivnuts a while back with stainless ones, and got one of the eBay Polish £30 undertrays, which fits fine. But finding the black T30 caphead bolts at a sensible price was another matter, and ****ty silver Allen-heads with big washers did the job meanwhile but looked wrong.
If anyone else suffers a similar degree of Alfa-OCD, you'll be pleased to know these are dirt cheap, and exactly what you need. £7.40 for 15 inc post is a lot better than £3.50-£4.90 each when you need 9 of them. Mine turned up from Lithuania pretty quick.
https://www.ebay.co.uk/itm/15x-TORX...NCIA-CITROEN-ALFA-ROMEO-46419734/121883124682
And use Copaslip, of course.