As suggested on twitter here is a port for iichid maintained at https://github.com/wulf7/iichid. How to use it can be found at https://larastechlab.blogspot.com/2020/01/i2c-touchpads-on-freebsd-130-current.html.
I'm more than willing to give maintainership to someone who uses it. Documentation is sketchy, hence very little here. I don't plan to put much more work into this than what is already here; anyone can claim the port for care and feeding.