Where to get some sort of ID for SN child going to festival?

[BoogleMcGroogle]

We've arranged to go to a couple of festivals in the summer (yay!). DS has severe verbal dyspraxia, so while he can say his name, explain he's lost etc. if he does get lost, no one will know what he's saying.
I've realised that this makes him quite vulnerable (even though he's not a wanderer as a rule). Does anyone know where I can get hold of some sort of 'if I'm lost...' ID? He is quite sensitive to items on his skin, so the less intrusive and harder to take off, the better!
TIA

You can get wrist bands like this on multiple sites, but he may not like wearing them? www.kiddymania.co.uk/identity-wristbands/single-use-identity-wristbands/please-help-me-i-m-lost-identity-wristbands-5.html

Or you could get large iron on labels printed which could be attached to clothing.

I have known parents write their number on a child's arm with a sharpie.

Thanks guys, laundry marker on the arm it is then. I suppose the one advantage of going to a festival is that there is no danger they might wash it off!
Love the idea of taking photos each day. We've never lost him before but he's getting a bit more confident now and there's always a first time....

I use silicon wristbands on DS (you can get personalised ones printed, in loads of colours from lots of sites), but there was a time when he would not wear them and we used engraved tags (like pet id tags) on a mini lobster clip attached to his clothes. I usually put both on him now, and have taught him to point to them if someone asks what his name is. (He also always has his minitablet with him, which has a sticker on it with my phone number).

For example, go to Amazon and look for The ID Band Company.

Or these
safeid.ro/en/

I always write on the arm. They quite enjoy it as I sometimes do pictures too