Might as well get one that works your cruise control. I had forgotten that there were two options, one for a Cabrio. It is the Roadster cruise control stalk however. It is a slightly different color gray but not noticeable. The connector is strictly plug and play, as I recall. I would order the stalk from Smart Madness. They might even have one in stock, and they may be willing to provide you with installation instructions with the stalk for the MDC cruise control. It has been almost nine years since I installed mine. So my memory of the install process is faded, but the stalk was one of the easier parts to install.
Here are the instructions and picture of the Coupe turn signal arm. For the Cabrio, it does not have a control for the rear window wiper which is why the Roadster turn signal arm is used.
Explain to Smart Madness that you have a Cabrio with the MDC cruise control and you need to replace a broken Roadster turn signal arm. That should be all they need to know. The arm in the instructions is for a coupe which is why it has the extra icon for the rear window washer on it. If you give them your VIN number, that will identify it as a cabrio as well.