I used to stress about this. Since my P250 has a flat floorboard, I could always use a paper carrier for short runs, but longer distances were an issue.
A friend sent me this great L.L. Bean Thermos -- actually, a double-walled aluminum flask. It holds about 24oz. of coffee, and will keep it nicely hot for about 12 hours. Fits under the seat, and has a carry bag that I can (if necessary) hang on the curry hook.
This thang is so good, I use it as a carafe every day, even when not traveling.
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