Upload & Sell: On
It is hard to find what you want at a low price. I too never found a low cost place to get metal shot, although I had heard that places that do sandblasting also do shot blasting, and may have used shot they might sell in the quanties we need.
In the past I have used fine rounded washed gravel that at least makes good use of the volume compared to larger gravel. But I know that is not really all theat heavy compared to steel.
The only other suggestion for something by tomorrow is to go and rent bags from a photo rental place to get by for now, which will leave you more time to decide on getting lead or steel shot, or just buying new bags that are pre filled.