You don't need to buy a specific external CD/DVD drive to use with the TurboTax CD. Any external CD/DVD drive that is compatible with the MacBook Air should work.
I have a number of MacBooks, and usually shop Amazon for peripherals.
One example I found quickly was at: https://www.amazon.com/Aluminum-External-Super-Drive-Apple-MacBook/dp/B007FUDKB4.
See the "Compare to Similar Items" section about half-way down the screen. This will show comparable items, with many positive reviews.
