DS has long legs and ginormous feet (yet is only 10th percentile for height...anomaly he is!) so we always had issues with him not fitting into onesies with feet properley. Bonds make leggings for boys (stretchies i think they're called) you can get knitted type ones or just the regular cotton, I've seen them at the supermarket. Then you can put thick socks on his feet and tuck the bottom of the leggings into them. When he was a little less delicate those blasted 'easy suits' were pretty good too, they have no feet or just some little trackies with the longsleeved legless onesies and a woolly jumper.