Leggins for slim DD

[YouStayClassySanDiego]

My 4 year old is very slender, I've bought her new leggings recently as she's had a growth spurt, so I've bought her the next size up, but they keep falling down.

Anyone got any quick fix solutions that doesn't require sewing?

I have to sew them, sorry! H&M are narrower, sainsburys and next seem really wide. DTs are in age 18 months to stay up at the waist even though they are nearly 4 - thyre rocking the cropped look!