This is a toughie, unfortunately you can't force a person, with bipolar out of denial, it usually if it comes at all, from the person him or herself.
If his mood(s) are or get mild enough, try to speak to him about this, and how you see a change in him, wishing he'd go for counselling, but try not to sound demanding if possible. You may even want to talk to a T first, they can direct you with some resources for info. and/or help you to know how to approach your husband. In the begining of my DX, my husbandd came to a few sessions, the psychologist spoke with him and I about the treatment options,etc., we even went to my pdoc together a few times, then as I accepted my DX, I went for therapy and med managment on my own. Let's face it many DXes are not easy to accept.
With the encouragment of someone in the mental health field, it helps cut back some of the denial, and often helps one accept,get treatment and move on with their lives.
Just my 2 cents.
I wish you lots of luck and love with this matter.

DE