$25 bucks
1 5 gallon can of gas.
Gas
1 Bic lighter
Those items do not do much to target a busload of kids in a school bus. But your list does serve to prove a point. Trying to stop all mass murder attacks by restricting access to weapons is a losing strategy.
The soft target for school bus riders is when dozens of children unload at a single stop (such as their school). It would be a good idea to make changes that restrict access to these areas or have armed officers on duty during loading and unloading.
But no matter what, it’s very difficult to completely prevent a determined murderer who has a death wish from random attacks.