You're never going to avoid lead entirely. Lead, arsenic, mercury, these are elements found in nature, concentrated in some spots more than others. Dolomite, being a common rock material, might contain lead, it might be relatively free of lead. Bonemeal, on the other hand, is only going to have significant amounts of lead if the bones came from an animal that was being poisoned by lead. In fact, bones are relatively free of lead and can actually sequester it as is shown in
this study.
Unless you are growing vegetables on top of a mine tailings or coal ash dump, I wouldn't be too worried about your plants picking up a problematic amount of it.