Please can someone help me find a black thorn bush?
If you mean prunus spinosa, which has the sloe berries used to make sloe gin, you may want to reconsider. It's on the USDA invasive watch list and is considered a weed in its native country (UK). Pricks from the hard thorns are not just painful from a puncturing standpoint--they're compared to hypodermic syringes--some people are also apparently allergic to the thorns, in a manner similar to poison ivy. Imagine that thing spreading around your yard!...yikes.
Anyway, sorry to preach when you asked for help...Oikos Tree Crops has it if you really need it.
Here is a link that might be useful: Oikos Link