After we picked up our rental car in Darwin in the Northern Territory of Australia, the blasting heat told us we would like a cooler full of drinks on our 3 day road trip through the outback. So we stopped at a Woolworths and picked up one of those terrible foam coolers, ice and some drinks. There was no bar code on the cooler so we wasted what seemed like 10 minutes in the checkout because the clerk wasn't authorized to ring up an item as general merchandise. (Hint to stores: I know you're scared of your cashiers stealing from you but this is ridiculous.)
It seemed to me that with a sizeable number of the renters in Darwin going off on outback road trips, who among them wouldn't want a cooler. So the rental company should offer a cooler pre-loaded with ice, and even perhaps some drinks. They would of course overprice this, but as long as it's not more than buying a decent cooler, people would go for it over those cheap ones, that can't keep ice long and run a risk of leaking into the nice rental cars in any event. There's other stuff that could go into the road-trip kit, ranging from walkie-talkies to umbrellas to snacks, too.