To anyone from the future, I answered my own question, as is often the case...
Using the spherical coordinate system
n = 32;
nc = round((n+1)/2);
vec = (1:n)-nc;
[x,y,z] = meshgrid(vec);
r = sqrt(x.^2 + y.^2 + z.^2);
psi = atan2(y,x);
theta = acos(z ./ r);
theta(isnan(theta)) = 0;
Mx = sin(theta).*cos(psi);
My = sin(theta).*sin(psi);
Mz = cos(theta);
quiver3(x,y,z,Mx,My,Mz)