My time is valuable enough that I would just buy certified lead from a supplier rather than toodle around all over trying to scrounge some. I have enough to get me through a minor bullet crunch, which is all I need.
If the hunt is part of the fun for you, have at it.
BTW, I've read that a lot of newer wheelweights are zinc, not lead, which may explain the hardness of yours.
It's pretty easy to separate the iron, zinc, and lead alloy wheel weights, but it is true that lead is becoming less and less common for wheel weights on passenger vehicles.
The best soft lead alloy in wheel weight form is in the stick-on kind that are found in little rectangles and strips of rectangles. Very low antimony/tin content, almost identical to pure lead. I use it interchangeably with pure lead.
