fish tank accessories (Emsworth PO10)

Hi, My Grandson 9 years old has rescued a Gold Fish - but we think he's a Koi. He lived in a tub for 5 years with nothing :( He has just aquired a new home as per foto. We would be very grateful if there is anyone local to Emsworth or Chichester town that may have some fish tank accessories in particular some hidy caves for him to rest in. I want to help my Grandson to take care of his pets, he's learning to clean him out & feed him. Thank you for looking & hoping to make one fishy very happy :)