Ray,
My last effort included a few layers of cardboard like what you would find on the back of a notepad in place of your Lexan. I used wire ties around the can to hold in place. It absorbed a little bit of MCU and made a nice seal. I also use 2 screws on opposite sides of the lid. One hole lets the Bloxygen in and the other lets the air out. I put a few drops around each top screw to ensure a seal.
Remove the top screws, then the bottom to dispense, replace the bottom screw, Bloxygen in one top hole for several seconds, replace both top screws, done. MCU storage is critical but not difficult. Just remember that whatever you removed from the can has a shelf life which is why I recommend doing batches with MCU.