That Deda stem's for road, right? I don't think they do MTB stems, anyways. Note that most of the stems already mentioned are 31.8. If you've a 31.8 bar already, you're in business. Otherwise you might wanna consider buying a new bar for extreme rise on a road bike bar. Typical 26mm road stems in hi-rise are quite rare.

Here's a 35 degree stem in 31.8.