Just got some Nitto mustache bars. Love the look and I think they can really work for me once I get a new stem (giving me back pain right now, too low). Rivendell suggests getting a shorter stem that is higher than your saddle and they recommend the Nitto Dirt Drop but I can't use that cos my bike uses a threadless stem. I don't know the first thing about components so does anyone have suggestions for a threadless stem that could work similarly? Or what kind of specs to look for?

Right now my stem is 70mm +/-10 degrees. I'm just regurgitating the specs I see but I have no idea what that 70mm is referring too. Little help?