Best way to humidify a large cooler

[smoke_ring]

I have a smaller cooler and am probably goign to buy a larger one today. I've used beads in the past but since sometimes I can't check on my humi for up to a week at a time they can run out of water or fill up too quickly and throws my whole thing out of wack for that period of time. My question is, what is the best way to humidify a larger cooler if you can't check it all the time, I know there is the oasis but I wasn't sure if there was any better options out there, thanks in advance.

Josh