There are probably a number of Luthiers that could make you one and to exactly your specification. I'm sure there will be plenty of suggestions to follow. Not sure if it would be cost prohibitive but I enquired a while back to have a custom neck made by Philip Porter in Manchester and he quoted around £300.
I know Mike Walsh, Zoot Bass, has done necks in the past and he is Kent way, so maybe not too far from you.