Deda makes both track drops and bullhorns in 31.8. They are 31.8 where they connect to the stem and taper off. I switch between both on my bike and I love them.
drops:
http://www.jensonusa.com/store/produ...r.aspx?sc=FRGL
Bullhorns:
http://www.benscycle.net/index.php?m...oducts_id=6853