AIBU? Really? All the shops seem to think so. Asda, TU, Tesco, Amazon, eBay, Debenhams, M&S - none of their websites have any grey jersey school trousers for a 9 year old girl.
I can understand individual shops selling out of stock in pre-internet days, but surely these big companies have a warehouse somewhere with more stock that they could link to their websites? They must know that children grow the whole year round.