the deda newton pista stem has an oversized clamp, so you would have to run their new oversized bars as well. the deda magic road stem has a fairly deep drop as well.

is this desired drop for form or function? do you have bars yet? you could just get a deeper track bar... such as the 3ttt, modolo or nitto b127 track bars. woodman makes a 17 degree drop road stem with a 26.0 clamp dia. that's fairly deep for a road stem. their site has the images for the 0 and the 17 swapped... but you get the idea.