Usually £5-9 on Amazon (or 99p delivered from China).
Not bad for only £1.25. Tesco Sandhurst had over a dozen still in clearance area. Only red left. Possibly nationwide. Instore only.
Wouldn't risk connecting to a PC USB (there is no protection electronics - just a DC motor and switch), but using with it with a Poundland USB power bank and it works nicely for 2-3 hours.
There's a heatwave coming. Stock up now :)