My most recent pass idea was a nice bookmark-sized pass that kids would place on their desk so that I knew who was gone at any given time. It was great, but....
An amazing first grade teacher at my school, and our buddies class, showed me what she used and it is BRILLIANT!!
Hand sanitizer bathroom passes! (I made the signs and they are available in Google Docs HERE)
I just cut out the signs and taped them onto the regular size of sanitizer. We ask parents for hand sanitizer at the beginning of the school year as a class supply, but I also see them on sale quite a bit throughout the year.
Now, when kids need to use the restroom, they move the pass to their desk and when they come back, they can squirt some sanitizer into their hands to make sure germs don't spread around the room at the speed of light!
I love the super-genius teachers in my building!