You can buy VSL#3 Probiotics from here: https://www.vsl3.co.uk/
Or you buy it from your local Lloyds Pharmacy (they keep it in their fridge).
Personally, I wouldn’t buy it from anywhere else, although there are sellers on amazon etc. It needs to be shipped in a chilled package and direct from the fridge. Also, VSL ship via tracked next day delivery.
Hope this helps.