The plunger is hard to get because it is only found by building or upgrading buildings. Here is one way to get them reliably:
1. Build 30 or 40 balcony apartments. This will probably get you a couple Plungers. (drop rate ~5%) It will also get you everything you need for a few Rental Agents.
2. Build as many Craftsman Homes as you can, based on how many Rental Agents you are now able to hire.
3. Fully upgrade all the Craftsman Homes. (drop rate ~15%)
4. Depending on your luck, this process should get you anywhere between 2 and 10 Plungers. As a side benefit, you should also get some Trash Cans, another hard-to-find item.
To get the Helicopter keys, simply upgrade your helipad or build one.
ways to get keys are as follows:
1.) Improved taxi Station
2.) Police station
3.) Logistics Center
5.) Luxury Home