Why don't you just develop a RR chufa and get rich? I'll finance the project, as long as it doesn't cost over $500 or so.
Interestingly, nutsedge isn't really controlled by glyphosate very well. It usually just will yellow it up but it comes back strong. You might even be able to spray 5-7 fl. oz/A over the top and hurt the weeds but not so much the chufa. Just an idea, I wouldn't try it on too big of a spot until I saw how they reacted. I have also seen research that showed low rates will stimulate growth on some plant species. Again, be careful if you try it.