Off-axis magnetic field strength for permanent magnet calculation/equation

I’m working on a project which uses cylindrical permanent magnets, and I’m trying to determine the expected magnetic field due to these magnets. One problem I run into is that these magnets are usually not completely horizontal above the point at which I want to calculate the expected magnetic field. Assuming the point is on the axis of the cylinder, it’s easy enough to calculate the expected magnetic field using the following equation:
$$B = frac{B_r}{2}left[frac{D + z}{sqrt{R^2+(D+z)^2}} – frac{z}{sqrt{R^2+z^2}}right]$$

where $B_r$ is the remanence field (found in a magnet’s data sheet), $z$ is the distance from a face of the cylinder on the axis, $D$ is the thickness of the magnet, and $R$ is the radius of the cylinder. However, this equation only works on the axis of the cylinder itself. How can I calculate the off-axis magnetic field for a cylindrical permanent magnet?

Note: I don’t particularly need the derivation for the off-axis equation for now, although it would definitely be helpful.