I’d just tell him it’s a present 🎁
I wouldn’t let him dispute it, because the bank can find out what it was and tell him and the surprise is gone anyway. Just tell him it was you and it’s a surprise.
I would have just told him you'd bought a present for him, if he disputes the bank will investigate and tell him anyways and then you've also wasted his time trying to get ahold of the bank
I also did a 1k purchase but went through PayPal so he didn’t know what it was exactly