"David D Stretch" wrote in
:

My 9 year old son, who is Chinese and up to 3 months ago had lived all
his life in Hunan Province, China, is missing being able to buy and eat
Dragon Fruit (Pitaya) in the UK, though I understand they can sometimes
be seen in shops.

Try Waitrose; they seem to have them fairly often.
There's one on my worktop at the moment (half price,
so I hope it is ripe