non integrated + stiff + narrow + cheap, you have aluminum. Wont be aero though. But i have a lot of friends who refuse riding carbon handlebars.
On aero, alu 36 or 38cm will probably make the whole system (you + bike) more aero than an aero 40cm bar. I dont think the drag of non integrated handlebars, given you have exposed cables anyway, matters too much. It would probably matter quite a bit with an integrated cockpit & full cable integration.