Without a mobile phone, how would you go about reaching roadside assistance or emergency services?
Any shitty old mobile with no service plan will work to call 911, as long as the battery's charged. A few people you know are probably tossing their old phones in the garbage every year, or you can get an old LG flip phone and a car charger for $20 on eBay.
As for roadside assistance, just take off your pants and stand in traffic! Someone will stop sooner or later.