Looking for designer jeans that fit your butt and your budget -- and don’t go against your better judgment? As any hipster worth her Earls will tell you, you’ll need to try on about a dozen pairs to find one that fits. This used to mean spending the better part of a weekend in a cab -- from Diesel on the Upper East Side to Helmut Lang in SoHo, with at least a half-dozen stops in between. But now, the would-be Sass & Bide -- or Earl or Roberto Cavalli -- girl can skip the legwork and head to Barneys. The denim department has all those lines, plus Daryl K, Marc by Marc Jacobs, Fake London, and more (prices are from $85 to $288). Styles on the “Jeans Wall” -- boot-legs, cowboy cuts, bumsters, tapered eighties numbers, you name it—are neatly arranged by designer, fit, and wash. The downtown Co-Op (236 West 18th Street; 212-716-8816) has a similar setup, plus an equally hip selection for guys, including everything from high-end Levi’s to snazzy G-Star, DDC Lab, and Red Ear styles ($80–$245).