I expect the original piece was steam bent, then machined with conventional woodworking tools. I hoped to find a replacement part at one of the suppliers below. I didn't see the exact part, but it may be worth contacting them.
http://www.lebaronbonney.com/
http://www.lebaronbonney.com/osc/cat...?cPath=469_532
http://www.thejeepsterman.com/
We do the steam bending for them.
http://www.barevillewoodcraft.com/