Thanks to television advertising, I hear "Mom, can we get that?" or some variation thereof, about 900 trillion times a day. No exaggeration.
Lately, I just say "Yes" every single time. If they press the issue, I tell them we'll get it for Christmas.
The good news is that it works! Conversation ends every single time. Can we get that? Yep. Cool, thanks.
It is so easy.
The bad news is that one day Christmas will come. I had decided when that happened, I would just start saying, "Yes, for your birthday" but I'm afraid one day they will realize that they don't really get this stuff, and it will stop working.