With this freehub body from Alexrims it is possible to convert your existing hub/wheel to HG 11-speed.

Anti-bite technology protects the lightweight aluminum cassette bodies from damage caused by the drivetrain.

Specifications:

Material: Aluminum/Steel
Cassette compatibility: HG spline L (Road 12/11-speed)
Compatibility hubs: Alexrims/Bear Pawls system
Wheel compatibility: Alexrims CF45, RXD3, CXD4, Boondock3/5, etc. 
Freewheel type: Pawl freewheel
Spring type: coil spring
Bearing: 2 stainless sealed bearings
Color: black/silver
Weight: