Find out how he feels about it and what it means to him to acquire one. See if you can catch the true essence of his desire for it, rather than whether or not the two of you will get one together. Reflect his feelings to him. Let him know that you understand his experience. When you are able to have a discussion, you will be faced with developing empathy for your partner's experience, separate from your own response.
Marriage is a partnership.
It is not magical. It is up to each partner to examine whether their needs are reality based and to withdraw any projection of their partner as Santa Claus. When partners feel powerless in their marriages, trust is damaged and intimacy suffers. It is important for spouses to be able to see themselves as equally responsible in filling their own and their partner's needs. Where these needs conflict is where growth happens in marriage.