How do I solve this equation--> iTunes + MacBook + Microsoft SYNC = what cheap, decent mp3 player?

My gf is now armed with all of the above except the mp3 player. I’d like for her to have an mp3 player in the car so that she can have all her music at hand (via SYNC), but it would be nice to just have it sync the content via her iTunes rather than managing it manually or with some other software. Ideally, the mp3 player would just stay in her car full-time unless there was a reason to put new music or podcasts on it. It seems overkill to buy an iPod for this purpose (not to mention, she would never use the player for any other purpose—e.g. she doesn’t listen to music via headphones), which is why I’m wondering if there’s a lesser brand solution. Also, the mp3 player would likely be plugged in full-time via a car charger.

I don’t know anything about other mp3 players and whether they play well with iTunes on a Mac. Ideas?

edit:: unless an old gen iPod makes sense… if so, what should I look for?