What to use??

[imkeepingeverythingcrossed]

I'm making a book for a child and want to stick a mirror in so they can see their reflection. But I don't know what I'm looking for or where to look for it?? Help me please. X

www.sensorytoywarehouse.com/product/mirror-flexi-sheet-a4-card/ - something like this?

Exactly what I was looking for. Thank you very much.