Mrs. Van and I have been together for 17 years and there isn't a week - sometimes a day - that goes by that she doesn't bring up something in conversation as though she were, literally, reading my mind, and vice versa. A little unnerving, but in a way that makes a person feel good inside.
What I haven't seen suggested, and there may be a good reason why, is to play out some type of "threesome" fantasy with your husband using a dildo or vibrator as the "third party". The implication must be clear, though. (Not the "real deal", quite obviously, but it may be another way of "planting the seed" carefully, as Mr. Naughty alluded to.)
Granted, it may seem like "beating around the bush", if you'll pardon the expression, but it may also open a window of opportunity for further discussion. Understand that it may also die right there, and be prepared to accept that. On the other hand...
(Personally, Mrs. Van and I adhere to VegasLee's admonition that sometimes fantasies are better left as fantasies. At least, I think we do...
)
Best of luck to both of you.
Van