Have you looked at the Nitto 115 or 105's? The drop is a little more than you want (140mm) but the 105's go down to 37cm and they have no grooves or anything. Very plain, old school bars. 25.4 centers but I've never had problem with Nittos in standard 26mm stems without a shim. My wife has these prefect bars on her Bianchi Eros Donna, they are super small Modolos but I've never been able to find a pair. Salsa Pocos are another option. The 36cm model has no grooves but they are anatomic 140mm drop.