Fiat main dealer accessory departments do a good quality tailored cab carpet. It's black with a waterproof backing and very hard wearing and a y embroidered Ducato on it. Has two fixing studs (easy fit) to keep it in place. Mine cost about £40 8 years ago and still going strong after some serious abuse.
but the Knaus chassis is Renault. It does have fixing studs which I used with previous rubber mats, but now the new carpets cover more of the cab area and integrate it better visually with the rest of the motorhome. I have put the rubber mats back and the driver one it cable tied to the steering column.