VW Heritage have them listed but available on backorder only, they're the cheapest new priced @ £62 ish:
https://www.heritagepartscentre.com/uk/1h0853986-cover-trim-for-the-sill-panel-rear-right.html
https://www.heritagepartscentre.com/uk/1H0853985-cover-trim-for-the-sill-panel-rear-left.html
There's the end cap for each side (£10 each) if they've gone too, and a black rivet for each.
VW Parts International had them listed on the eBay shop they have, but sold out at mo, they were £77 a side.
Second hand good ones are scarce, there's some sellers in Latvia (but not used