Many Airstream owners I know carry small gas generators in their tow vehicle, typically Hondas or Yamahas. There aren't very many places to put a generator in your typical Airstream.
Having said that, we met a guy at the big Oshkosh fly-in a couple years back who'd mounted a huge generator under the bed of his 31' Classic. He was unusual in many ways, including towing that beast with a BMW SUV (And I'm not impuning BMWs; we've owned several, but we've driven an X5 and wouldn't want to tow a large Airstream with one.)
Not sure I'd be able to tolerate the noise, vibration and fumes of a generator under my bed, but he seemed to still be breathing.