Your solution to the isopropyl alcohol evaporation problem is a good one. Thanks for sharing with us. I thought I would present my solution here in your thread.
I decided to look for a container that the tank would fit into. This army ammunition can from ebay is doing the trick for me.
I had to replace the seal with a new piece of 1/4" rubber so it could hold back the 0.7 psi of vapor pressure.
The ammo can lid is 15" by 12". That vapor pressure would result in a force on the lid of 126 lb. It really adds up for a container this large.