Hertz - Snagging a convertible at SFO?

Any suggestions on how I can get a convertible at SFO on Sunday evening. I'm renting the car for 4 weeks and would really like a convertible - but if I up to the convertible rate, my company won't reimburse me ANy of the money (not good). So right now I'm stuck with a Taurus. Any ideas?

Using priceline you should be able to snag a convertable at a fullsize price. Would your company be OK with a priceline receipt?

You can also try Hotwire and see if their rate is low enough for you.

Here's a hypothesis.

Perhaps the chance of getting a convertible would be higher at a non-airport location.

First, non-airport locations stock fewer cars. This would cause a higher variability of cars of each class rented. Thus these locations might be more likely to run out of your class.

Second, a location like Fisherman's Wharf would cater to tourists. This would cause them to disproportionately stock tourist-friendly cars like economy cars, convertibles, and minivans. Tauri might be in shorter supply, thus increasing the chance of a bump. It should be easy to refuse a minivan/SUV bump.

This is just a theory. I have no experience doing this at all. (Got a convertible Mustang at SFO once, but didn't do anything special to get it). Anyone know if this makes any sense at all?