Can't think of anything I would have a use for a piece like that. When, and if, I ever finish my banjo I will be making a case for it and will just set it in the case.
However, if I did want a piece shaped like that it wouldn't be that hard. I'd cut the end profile wanted out of plywood, ether 1/2" or 3/4". I'd get it perfect, then glue it to a rough cut piece of plywood, then use the finished part as a master, and rout the rough cut piece. Then glue the two to another rough cut piece, and rout. Repeat until you get a length you want. It can be done, I've done similar. And when you put a finish on it, the plies will really pop. You could use solid wood also, but I like working with plywood. Just keep your fingers away from the whirly part.
"It ain't what you're told, it's what you know." - Granny Weatherwax
Gather the villagers, pitchforks, torches; we march at dusk!
Some days, the supply of available curse words is insufficient to meet my demands.
.....Call me a craftsman, artisan, or artistic, and I will accept that. Call me an artist and you will likely get a quite rude comment in return. I am not a @#$%ing artist.