I found a previous solution which was a custom shader that works exactly how I want it to, however, the shadows that are cast on to the object are completely black with no way to adjust them. I have no experience with shaders so not sure where to start or what I need to implement so any help is appreciated.
Previous forum post:
https://polycount.com/discussion/125797/unlit-with-shadows
Replies
See also the video series from Ben Cloward.
check it's custom toon lighting sample.