Waist harnesses a different for different people so its impossible to recommend a specific harness, I have found the ones that have the extra strap to hold the spreader bar down work better for some reason
. I know the Dakine has been said to be a bit stiff, maybe try a softer harness????
I will also say that a harness riding up is rarely, if ever, to do with the harness and more to do with the technique of the rider. I do understand where you are coming from as it took me 2 years to get used to a waist and not have it riding up but now I have the technique I can wear any harness without it riding up.
Lean back, hips forward, use your legs more and keep the kite lower, can still get pulled up after a crash etc but always will
you want the kite pull perpendicular to your body and not upwards.