Would it be fair to say "they were out" and then give the item as a gift?

My Dad has been pining over a wireless security camera kit for a while now, and his birthday is coming up. My siblings and I are thinking about getting it for him as a birthday gift, but he has a tendency to pick up stuff he wants himself.
I’m heading up this weekend, and my dad mentioned he might have me pick up something from MicroCenter and pay me back when I get there.

Would it be fair to pick it up, tell him they didn’t have any when I was in, and then give it to him a few days later for his birthday?