There are some campgrounds which locate the power pedistal between 2 rigs sitting side-to-side (I guess to save $'s). In this configuration, there may be times when you may need an extension.
As Cliff mentioned, carry a 30A 25' extension cord with a 50 to 30A dogbone. You won't have as much wattage (3600 watts on 30A vs 12000 watts on 50A) but you should be able to get by, even using A/C. This will at least give you some flexibility with not as much $'s invested for the few times you may need it.
'07 Winnebago Journey 34H - CAT C7, Koni's, MCU's, SS Bell Crank, Safe-T-Plus
'07 HHR Toad, SMI AFO, Blue OX