Convertible car rental

Kind of random, but a friend of mine emailed wondering where she could rent a convertible. She wants to surprise her husband for his birthday. Can't drive stick, otherwise I'd just let them borrow mine. Any thoughts? Seems like most of the big chains offer them, but only in sunny areas like LA and Hawaii. I was able to locate one place that rents Ferraris, but a less high-end option would be better.