I have one, but not like the OP it's because I like puzzles, and unlocking a lock is a puzzle to solve.
It has spoiled some TV watching, I have been known to say, "No, that's a yale, use a rake" when watching Hustle.
OP I got an electronics kit at about that age. Mine was quite a big one with springs but you can get the boards and wires separately. So you could start with a small kit, maybe to make a radio or a 'buzz off' game - easier to do with a light rather than a buzzer.
This one looks like you could make quite a few things but is not exactly stocking filler price
https://www.amazon.co.uk/ELECFREAKS-microbit-Starter-Kit-Micro/dp/B09QPVC3WT/ref=sr_1_43?crid=JWB28P19B899&keywords=Electronic+Project+lab&qid=1695526591&sprefix=electronic+project+lab%2Caps%2C123&sr=8-43
BBC microbit might also be fun - it's actually a computer
https://www.amazon.co.uk/GeeekPi-BBC-Micro-Development-Programming/dp/B0BB949JCP/ref=sr_1_4?crid=1LYDNK8W4068G&keywords=bbc+microbit&qid=1695526823&sprefix=bbc+microbit%2Caps%2C121&sr=8-4
Do they have top trumps?
Rubix cube?
I know they are old but they are still entertaining.
I got a friend a mini arcade game that plugs into the tv and has a joystick, we spent hours playing packman, there were 3-4 other games.
Some kids love old tech, things like an old dictaphone with mini cassettes.
Years ago a friend's mother moved to an old house that still had a dial phone, my friends kids thought it was wonderful.
I've just remembered I had a kit to make a pin hole camera and camera obscura.
And I built a calculator.
Another thing, not a stocking filler, is a polaroid camera - mine is very popular with children at my family gatherings.
I was a geek before geekyness was even invented.