Ask your husband if he is into **********, then bring home a girlfriend to share.
Certainly, ask your husband. Most men have a secret (or perhaps not so secret) fantasy about seeing their wives with another woman. If he agrees, just make sure to establish the ground rules up front: are you comfortable with him watching? Do you want it to be strictly lesbian, or do you want your husband to join in? If the latter, will your husband be limited to only interacting with you, or will you permit him to have sexual contact with the other woman as well. Just set up your boundaries in advance, and be willing to compromise, and things may well just work out fine. Good luck!