Struggling to find dungarees to fit, Anyone else?

Hey my baby is only just 7 months old but on the bigger side.

I bought some lovely 6-9 M&S dungaree set from Vinted and it is way too tight on her legs and too short to do up under the nappy.

I then bought a gorgeous Next floral one from Vinted in very good condition in a 9-12 size and it’s the same. It’s popping open under the nappy and legs are tight.

I get that secondhand can shrink but this seems ridiculous, they’re both unwearable but both outfits I’d actively choose for her to wear.

Does anyone else have this issue? Any other brands that are more generous in sizing? They seem too short in the body and leg, but they’re roomy at the top, so I assume 12-18 will be too big.

Help!

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