DS keeps un clipping his 5 point harness in the car... Is there anything I can buy to prevent him being able to?

[2point4kids]

He is only 2 years old so not really old enough to reason with very well.
I have told him it is very dangerous and not allowed. He seems to listen but forgets very quickly and un clips it again.

He is in a stage 1 carseat with a proper 5 point harness.
Is there anything I can buy that will cover the clip or prevent him from being able to open it so easily?

Have looked on Mothercare etc websites and cant seem to see anything suitable.

Thanks!

There is nothing as they aren't considered safe.

does he have anything in the back to distract him or is he a thrower?

He does look at things sometimes, but he can also be a thrower sometimes, so I only tend to give him things to play with on long journeys.

To be honest, giving him something to hold would make it worse as he is un clipping the belt to get out and reach things etc if he drops them.
I also have a baby in a stage 0 carseat in the back too and if the baby cries/drops his dummy then DS1 is out and trying to help him.
He isnt doing it to be naughty. He just see's things he want to get/do and forgets he isnt allowed to open the belt.

Is there nothing at all that they sell?
Surely it is more safe to have something covering the clip than to have him bouncing around the car?

this has a cord to attach the wheel to his car seat crotch starp, so it doesn't go anywhere

Thanks.
I never thought of a toy but that could be a good solution.
I have a Mothercare near me, so will go and have a look.