Another topic to investigate for this is "dark therapy." (At least, I think that's what it is called.) It is a process of regulating brain chemicals by restricting the number of hours of daylight a person is exposed to (sort of the opposite of Seasonal Affective Disorder), and it can be done by using special (expensive) sunglasses or even the kind of (inexpensive) goggles that are used with some types of mechanical work (maybe welding). I think they have to be amber-colored, but I'm not certain of the color.
It is definitely best to have a doctor help with this, because different BP sufferers need different amounts of darkness; some might only need to wear the glasses/goggles for 6-8 hours per day, but some might need a whole lot more, and only a doctor can help figure that out. I believe it is also important to maintain the same schedule, the same hours of light and dark each day. That is, just having 6 (or however many) hours per day is not quite enough; they would need to be, for example, 7PM-11PM and 6AM-8AM each day. That's an example only.
Try running a search on "dark therapy," "bipolar," and "goggles," and see if it gives you some information. I don't want to imply even a tiny bit that this is done totally without medication. The use of medication or not, or any kind of therapy for that matter, is something that absolutely needs to be decided with the help of a competent, trusted physician, preferably a psychiatrist!!