I got some that look like what you want from ebay after breaking a few when taking my arch liner off, the metal speednut was for one of the screws at the bottom edge as it had rusted. The plastic push pins worked on the front and rear, the hex nuts I bought years ago and don't remember seeing them on the weelarch but I seem to recall some plastic threads snapping off - was it for them?
I haven't tried all of them yet.
https://www.ebay.co.uk/itm/10x-Trim-...0/371853734384
https://www.ebay.co.uk/itm/5x-KUNSTS.../181699968556/
https://www.ebay.co.uk/itm/Speed-Fas...p/322352260488