Running shoes for DS (10) who has flat feet...help!

[nobodysfool]

Hello my DS has asked to start running. He has hypermobility and has orthotic innersoles in his normal shoes.
I can see online that there are LOTS of running shoes for flate footed people but struggling to find some for him (size 4). I don't want to spend a fortune (yet) incase he doesn't enjoy it. Any ideas where to look for a decent pair?
TIA

Do you have a decent sports/running shop near you? They can analyse someone's stride and make suitable insoles there and then.

Thanks for your replies.
We have asked if we can have or purchase duplicate innersoles but they said no.
DS has the innersoles had only come about 3/4 of the way down so removing the innersole wouldn't work for him.
Will have a look at Asics, thanks.

DS also has flat feet, orthotic insoles and is a keen runner.

Luckily we have a specialist running shop near us so DH took him there and he found some Brooks trainers that suited his feet/insoles in size 3. He'd previously had Asics but they didn't offer enough support at the side of his foot.

We were told to choose a shoe with a flat bottom inside so that we can put his arched supports on that rather than trying to fit one arched insole on top of another.

DS's insoles are wide enough that they are a snug fit and don't slip when he's running. We were advised to only have one pair at a time until his feet stop growing.

Thanks Oldbeanbagz - Can I ask if your sons insoles are the solid type foam. His current ones are loads of bright colours and feel quite firm and I wonder if they are suitable for running or if they would be too firm to flex?

DS's ones are quite hard plastic (?) molded to his feet at a private podiatrist. (NHS waiting list was long plus DS takes his running very seriously)

He first built up to wearing them by adding an extra hour each day and then started running in them 2 weeks after first wear. They're fine in his running shoes, there's enough flexibility in them.

Women's ranges start from size 4, with a few starting smaller. I can't help on particular models, but there's a lot of unisex colours out at the moment.