There must be some way to backup purchased audiobooks from my iPhone to my reformatted Mac.

I reformatted my MacBook Pro about a month ago, and have recently tried syncing my iPhone 5s with iTunes on my MacBook Pro, so that I can temporarily remove some purchased audiobooks, in order to make room to sync over some other audiobooks that I haven't listened to in awhile.

However, you guessed it, if I proceed with this process to add additional audiobooks to my iPhone, I get the warning that all music, books, audiobooks, and photos will be removed from the iPhone. That's not an option. I know that iTunes purchased audiobooks are one-time downloads, unlike purchased iTunes music. Since I have purchased two expensive audiobooks on my iPhone, since the time that I reformatted my MacBook Pro, I am not willing to double-spend in order to buy them again. Nor, I am willing to lose these books. I'd like to re-listen to them monthly, for the foreseeable future.

If I were to try using a backup of my iTunes library (from just before the MB Pro reformat), it wouldn't include those recent audiobook purchases.

Is there a proper method to achieve an up-do-date merged sync, and not lose any audiobooks? If not, is there a reliable third-party software or system I could use? I'm hoping for something above the worst case scenario of simply playing the audiobooks from my iPhone, and recording them into an mp3 using AudioHijack Pro on my Mac.

This has been the only glitch in my drive reformat issue.

Thanks for any help you can offer!!!!