There are only a handful of companies making cases and bags for the current-generation Mac Pro, including Tenba with its Air Case for Mac Pro ($440). It’s definitely not cheap, but then again, it’s a protective carrier for a machine that costs a minimum of $3,000—it may be worth it to spend a few bucks. While most people will leave their towers at their desks, pros on the go could very well need something like this, whether for carrying…