PE kit keeps getting lost

Hello, my name is Amy, lovely to 'meet' you all.

My son started at grammar school in September. For the most part, he can coped really well with the transition. However, he is finding it really hard not to lose things, mainly PE kit. Does anyone have any ideas to support him with this? The school are just saying he can leave it in a designated area, which doesn't really help, as he is forgetting to puts things back into his bag in the changing room.

Many thanks, have a lovely day.