plastic trim

I recently noticed that on my 2013 Leon 5F this plastic part is broken. It resonates when driving and it's kinda annoying. Any ideas how to fix it?

Hey, When I bought my ibiza, there was some plastic trim missing which shows the metal mechanisms on the side of the front seats. It's been doing me head in since, so I went to find the part numbers to replace them. Luckily, there was a piece of it in the boot (left side of passenger seat)...