Jason,

Buy some velcro strips, put one side on the lid, the other on the humidifier case and BAM! Remember, you might want to air out the stick'em on the velcro, so once attached, leave the humidor open for 30-60 minutes. Probably doesn't make a difference, but better safe than sorry.

Besides, you don't want to ruin any ISOMs you have, or Bolivars for that matter