There are several directions you could go with this. The Germans's make several solid options, VW Eos or Bug are fun options. Then there are of course the BMW/Audi/Mercedes midsized convertibles which you can probably find used in your price range. These might all be higher costs to maintain, but at only driving a few thousand miles per year, they will be plenty reliable.
You might look a little outside the box. The Jeep Wranger is actually a really fun convertible and they hold their value extremely well. Nissan also made a strange but interesting Murano CrossCabriolet convertible. They didn't sell well, so you can get them lightly used for very cheap if you can find them. There is also the old standby Mustang convertible.