IronHorseDriver

Hello folks, It's been years since I've designed any electronic circuits (I graduated from HS electronics 25 years ago), so I'm a bit rusty in this realm. I want to make a simple auxiliary battery pack, that can use 4 AA batteries, to run an MP3 player after the internal battery runs down (I am going on a long overseas flight and the flight duration is much longer than the battery life of the MP3 player). Trouble is, the output of 4 AA batteries is 6 volts, and the input voltage of the MP3 player (a Cowon iAudio X5) is only 5V. I'm not sure whether the 1V difference will cause a problem, and I already e-mailed Cowon Technical Support to enquire about this. I know I can use NiCads, which have a 1.2V output, but I have a bunch of fresh alkalines at home and would prefer to use them. I was thinking (mind you, it's been quite a while) of placing a 5.0V zener diode across the output, but I think that this will cause a constant drain on the battteries. Is there a better solution? Preferably, one that will not cost a lot of money in components, and with the parts available from Radio Shack. Additionally, if anyone knows of electronic component supply outlets in the Chicagoland area, kindly advise me. If anyone can provide assistance and/or e-mail me a rough circuit diagram I would be most grateful. Sean