Vinyl Siding

We lost a section of this vinyl during Hurricane Florence and no one seems to be able to help. Our replacement window are certainteed and the siding guy says it's a window part. It sits just under the window between the window and the sill. Is it weatherstripping? Can you help me get a replacement piece. There are four windows and we could use another similar product and do all four if we can't get the same exact piece. I have included pictures of the window and you can see the gap where this piece belongs
Thank you so much for your help!