As far as I know, all mountain bike bars are going to be 25.4. I would advise buying a 25.4 stem (any mtb stem, some nitto road and track stems) and any old mtb riser bars. If you already have a 26.0 stem, buy any old mtb risers and shim the bars with a beer can. If the beer can shim disturbs you, Nitto makes some fancy stainless steel shims to allow you to run 25.4 bars with a 26.0 stem.
http://www.rivbike.com/webalog/handl...ape/16095.html

On a tangent: I often see deep drop stems paired with riser bars. I hate that. Buy a stem with less drop and run a flat bar. You can get the exact same hand position with less weight. If you want a sturdy and swept back bar, buy a surly flat bar.