I use Zip Lock weather shield cases. They can perfect for placing in foam troop on the bottom,and the vehicles on top of those.
Or get smaller ones and just have on for your vehicles, they holder a good amount, place a small sheet of foam on the bottom 1st.
Here is a taller one https://www.amazon.com/Ziploc-WeatherShield-Quart-Storage-Clear/dp/B00MWTJXP0/ref=sr_1_2?s=home-garden&ie=UTF8&qid=1539587231&sr=1-2&keywords=ziplock+weather+shield&dpID=41xSHNYCloL&preST=_SX300_QL70_&dpSrc=srch
Here is the shorter one https://www.amazon.com/Ziploc-WeatherShield-Quart-Storage-Clear/dp/B01M9CHXGX/ref=sr_1_8?s=home-garden&ie=UTF8&qid=1539587231&sr=1-8&keywords=ziplock+weather+shield