“THE Nanny Diaries” bombed, but the market for chick-lit movies is still hot. Isla Fisher has just signed on to star in “Shopaholic” – based on Sophie Kinsella‘s book series of the same name – which starts filming in January, presumably after she has popped out Sacha Baron Cohen‘s baby and lost the weight. Director P.J. Hogan was already scouting locations last week and toured the W magazine offices looking for an appropriate site.