I got my three flower girl dresses at 16 dollars each and they are cute, but they are not fancy or dancy enough

They are basic white with just a bow around the waist. I found out my cousin with daughters (who've already been flower girls several times) are getting their dresses custom-made in our colors.
SOOO, I don't want my three cuties to not look special enough so I am trying to MAKE tutu-like petticoats and dye them fuschia-- one of the colors. Anyone know where I might find slips/petticoats for girls under 4? I have only tried Mitchell street shops and they just had the elaborate dresses and hoop skirts.
Open for ideas! TIA!