Hello I'm using this one.
bluetooth mini keyboard bbk200 beewi
Features Bluetooth Version: Bluetooth 2.0 + EDR
Range: 10 meters (Class 2)
Talk time: 60h
Standby time: 400h
Dimensions: 114mm x 60mm
bee-wi website to see more
same area as the X10
but it is no longer available on the site where I bought it
PS : not compatible with E10i [X10 mini] 'edit' :
as Default Official ROM but not sure.