School Trousers, help..?

I like the school trousers that are skinny lyrca material. I used to buy them from Blue star, but they don't fit me anymore, i'm a little over 5ft8 and so i need them quite long, i like them tight and they must be black. So, the last year i have bought them from topshop, but now they've stopped doing them they only sell the cotton straight leg ones. Where can i buy some black, tight, stretchy trousers from? (From the uk only please.) thank you :)