Advent Calendar fillers for boy, 13

[Veganator]

I have been filling in a wooden refillable advent calendar for my son since he was born, but now he's 13, I am out of ideas! They need to be quite small to fit in the little boxes (about 7cm x 7cm). Not food. Not crazy pricey either. (Ideally under £20 for a set of 24 things!)
And yes, he's 13 and not a young child, but his little sister will be getting hers filled, so I can't leave him out (she believes our elf on the shelf fills them every day).
tia

What about Lego, or alternatively the actual money in different amounts up to your total budget? If you don't want to do food, then I think cash might be the only option for this age that will definitely be used. My DS always likes a chocolate advent calendar, but has also liked Lego and would certainly use money!

You can get bundles of little figures if he likes things like Pokemon.
Tbh food is easiest but a daily 50p would probably go down well.

Thanks, both, for replying. He does love money!!! Don't we all. Stil, I'd prefer he had a little token something, like his sister.
Where's the best place to get little pokemon figures, or similar?

in the past I have filled my sons with

legos
glass marbles
pretty rocks and minerals
semi precious stones
fossils and shells
insect resins
wooden stamps

Thank you.
Did the rocks/minerals last year (big hit!).

Tempted by the fossils! Off to hunt!

What do you mean by wooden stamps? Can you post a link ti the kind of thing? Thank you.

they are rubber stamps with wooden handles, although that was when my son was youngger, you can buy them online or in craft shops. I got them from Flying tigers a few years ago.

Ah, I know the things you mean! Thanks!

My kids share one. I used to get them tiny toys when they were little but now they are 12 and 14 they get 3 things:

1. a chocolate coin.
2. a tiny Christmas decoration that they hang on a wooden tree, with the star for the top on Christmas Eve (got it from paperchase years ago).
3. A note with an activity on it; sometimes activities, such as Panto or Christmas baking, sometimes "lucky dip" where they pick a larger present (some recycled, such as the same Christmas jigsaw every year, or a bag of sweets etc) which is wrapped and put in a big bag full of polystyrene beans.

They love it and it isn't very expensive as most things are recycled each year.

Thank you!
Yes, my two share the one advent calendar, I just need to think of something to put in it for my son. Daughter is easy. She loves cute little things, toys etc. He is 13 and not really into anything other than gaming and sport, but doing sport rather than needing any stuff.

I'm doing this for my son who is 12, so far I've got hot chocolate sachets, mini jam, lip balm, face masks, temporary tattoos, marbles, unusual balloons, funny rubber, mood ring, coffee sachets, those rubber grip things they put on PlayStation controllers, mini nail polish, face serum. Most of these bits were from poundland

Thanks for the ideas, @DangerousMouse

I shall post the ideas I have got so far for mine (boys and girls ages 16, 14, 10, 8)

1 marshmallow matchbox
2 hot choc sachet and marshmallows
3 bath bomb
4 make button snowman
5 personalised decoration
6 Xmas pen
7 ticket for some Christmas thing
8 face mask
9 xmas cookie
10 mini donuts (cheerios dipped choc/sprink
11 crystal

This was just copied and pasted from my notes so happy to clarify if Abby are unclear!