While there are no known analytic solutions for force-free magnetic fields in toroidal coordinates, with a reasonable boundary condition it is possible to find a solution for the surface field and, with a restriction on the form of the field, to the interior of the torus as well. Published in Physics of Plasmas (vol. 30, Issue 5); online 17 May 2023.
Here is the link to the paper:
http://www.gemarsh.com/wp-content/uploads/POP23-AR-00182.pdf
A FORCE-FREE MAGNETIC FIELD IN TOROIDAL COORDINATES