Check out the various cast bullet manufacturers. A bullet cast out of the equivalent of the Lyman #2 mix, along with a good lube should work well. Avoid bevel bases. A flat base bullet will work well a long as the guns throat, forcing cone, and bore are all within spec. A lot of shooters use gas check bullets in the .357 to avoid leading. Swaged (pure) lead is to soft. You want enough hardness to minimize leading, and ensure expansion while avoiding a bullet that fails to expand, or breaks apart because it is to hard.
Larry