Clothes sizes

So my daughter was born 6weeks early weighting 5lbs 11oz and 19” long.: she is now 6weeks old and 6lbs 6.3oz and 21.5” long.. newborn clothes are to short for her but fit but 0-3 is to big in both ways.. onesies in newborn still fit and have room it’s just pants are long but not tight to her they fall off still.. 0-3 just fall off.. is there a brand of 0-3 that run smaller that I can get her