i don't have a picture either but like HFarr said you can buy the hdpe anywhere, then buy some foam from a furniture shop or online. The vinyl you can get from a local shop that does boats. Just bring one you have and see if they have some vinyl that will match. I have made a few back rests for the bow this way and they turned out ok.
Scott
2021 Craz
2007 Mobius LSV
1997 Sea Ray 190