我习惯了会在里面穿一件吊带背心和一条bike shorts作为打底。

bike shorts 请参考，只要都是纯棉的就可以了：

http://intl.target.com/p/girls-bike-shorts-cat-jack-153/-/A-51691456

http://www.gapcanada.ca/browse/product.do?pid=167103033&vid=1&locale=en_CA&kwid=1&sem=false&sdkw=gapfit-kids-bike-shorts-P167103&sdReferer=http%3A%2F%2Fwww.gapcanada.ca%2Fproducts%2Fgirls-gapfit-bottoms.jsp