right i know this is a lil more than you wanted to spend but look at this.
http://www.ebuyer.com/UK/product/125733
again this is in the uk but im just pointing out that its only £40 and that is extremely cheap look around for something like that in the us i know the mp3 player is only 512Mb but im sure most car journeys will not last longer than.
song size 3 Mb each
total size 512Mb
songs 3 mins each
512 / 3 = 170 songs
170 X 3 = 510 mins
510 / 60 = 8.5 hours
lol now i know thats alot of info but basicly do you regulary go on journeys over 8.5 hours ?
n e ways look out for a cheap 1 in the us