Swings without timer?

My son has acid reflux and refuses to sleep in his crib. I have the fisher price snugabear swing that he sleeps in. One thing that sucks is that it shuts off after four hours which might prevent him from sleeping longer at night. Well we are going on vacation for a month and I need to find a portable swing without a timer. Do they make any swings without a timer? Any suggestions? Thanks in advanced.