Option to show perpendicular guideline when creating gradients

It would be really helpful to have an option to show a variation on the gradient cursor with a perpendicular line to the direction of the gradient. I spend a lot of time drawing gradients up to the edge of products in photographs, and unless it's a 90º or 45º angle I have to just keep eyeing it until I line it up correctly. The image attached isn't the best example of this but does show what I'm picturing.

Apologies if this is possible and I haven't managed to find it ..!