08/17/2011 at 11:00 AM EDT
dropped some serious cash – $506! – for a silk kimono from Nicole Richie
's Winter Kate line
while shopping with her daughter at Sofia Boutique in Chicago. The singer tried on various dresses – a combination of new and vintage – but left with the coral and sky blue kimono and a free T-shirt gifted to her by the boutique. She also signed the store's dressing room wall – and was "very pleasant and beautiful," a source tells us.