I think any kind of riser bar should help you out, but what you end up with is going to be highly dependent on your budget and riding style. You can easily spend over a hundred bucks on a pair of handlebars.
You'll also need to find the diameter of current bars, to ensure the new ones fit your stem. Yours should be either 25.4 or 31.8 mm (more likely 31.8 for recent builds). I suspect you'll find a lot more riser bars available in the 31.8mm size.
If 20mm rise is sufficient and you have a 31.8 mm stem, these are on sale. I'm currently riding crank brothers' cobalt 3 bars that only have a 15mm rise but they are perfect for me. I have friends who swear by Easton's monkey bars like the EA50/70 as well - these are available with 20-40 mm of rise.