Found this, not sure if it is any use to anyone. It is a smaller size than the new dyson vacuums.
See photo for ref numbers.
I cannot check if it works as we don't have a charger to check. I assume it does as I am sure we would of disposed of it.
A small sized dyson battery (Street on the Fosse BA4)
This offer has been gifted to someone and is no longer available.