Probably not what you are after if you are going with the minimalist look, but if you plan on having a passenger for any length of time, I'd recommend these:
http://www.amazon.com/Rivco-Products-Adjustable-Passenger-Floorboard/dp/B0067EXXMA
Not cheap, but my wife loves them. They allow her to adjust easily at any stop, with no tools.
http://www.amazon.com/Rivco-Products-Adjustable-Passenger-Floorboard/dp/B0067EXXMA
Not cheap, but my wife loves them. They allow her to adjust easily at any stop, with no tools.