Try either of these
sensors, depending on what you need

http://www.ebay.co.uk/itm/2-X-BMW-PARKING-SENSOR-PARKSENSOR-E39-E53-E60-E61-E64-E65-E83-MINI-R50-R52-R53-/191550770489?

http://www.ebay.co.uk/itm/2-x-BMW-PARKING-SENSOR-PARKSENSOR-E39-E38-E53-E60-E61-E65-E83-Z4-EINPARKHILFE-/181707478201?