DS has a ridiculously small middle - he's 20mo, but 12-18m trousers fall down, so he's in 9-12m onces, but they're getting a bit short (obviously!). Where can I buy slim-fitting 12-18m trousers (I can't imagine he'll need 18-24m ones for a year yet - he's had one pair of trousers that have fitted him since last Christmas!)? I've found Next to be quite slim-fitting, but even those are too loose for my slim jim!