If there are any helicopter operators in your area, have a word with someone there.
Tungsten is very commonly used for main rotor blade, tip weights. (because of the very high density, it helps give the blades high inertia).
Once the blades are time expired, they are usually cut into scrap.
These weights are fairly sought after by sheeties, as they are very good for riveting blocks, but you might be lucky. (especially if the transaction involves a few tinnies!)