Well, here's what my dh did when he bought the dishwasher I didn't think I wanted ...

dh (calling me at work): Uhhmmm, I have an admission to make. I just bought a dishwasher.
me: Oh well. Bought is bought.
dh: So you're not mad?
me: Not much point in being mad now, is there?
dh: Ok, then. NOW I'll go out and buy that dishwasher.

Think that might work for you? In this case it had to be by phone. DH can't carry off a lie face to face.