We started the snow bird trip without one and discovered that 10 lbs of ice in a bag takes up 1/3 the freezer space. The Sahara normally has an icemaker built in, but ours was removed by the original owner.
We bought an Igloo from Walmart (couldn't find one in a store so we got it online). Takes about an hour to make a 1 gallon Ziplock bag full of ice. It only makes the ice; you still need to put it in the freezer to keep ice. However, we tuck that Ziplock bag in the door compartment in the freezer and it takes up no room in the freezer.