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I rented via Elite Motorcars - Elite Rent-a-Car: luxury car rental and limousine service all over Europe white glove service - top notch - they delivered the vehicle to me. They are based in Switzerland and I used them as that was my departure point. Make sure you ask for an Autobahn Vignette if traveling inter-country (Austria). Sure, you can buy them at a gas station, but why stop at a gas station?
Oh, one more thing - Tesla Superchargers are everywhere, but so are other brands - most of which allow you to use a credit card - so don't fret about finding a place to charge.