Lamb Leg is the traditional name in United States. Outside that tradition, butchers carry comparable lamb cuts under different names — sometimes the same anatomical piece, sometimes a close cousin. The alternatives below are grouped by country so you can match what your local butcher actually carries.
The chump is the rump end of the leg, so leg steaks cut from the top of the joint are the nearest larger-format substitute.
Same primal — the shank is the lower half of the rear leg, sold separately when the leg is broken down for retail. Whole leg is for roasting; shank is for braising.