Buckingham Caddy - grey clip on tray for Zimmer frame (Cornhill on Tweed TD12)

I’m trying to find a ‘Buckingham Caddy’ it’s a grey plastic tub that has a lid that doubles up as a container to carry bits and with the lid on it becomes a ‘table’ just big enough to carry a cup of tea and some little bits. It clips onto an ordinary zimmer frame and makes it easier to get a drink or something to eat and get back to your chair. It’s for an elderly neighbour.