If you need much longer consider one of the older model Sony MP3s. Look on their website and you can find a model with FM radio as well. I have one without FM that last up to 25 hours on a single USB charge.
I happily run with a sony. Been through 4 in the last 5 years (all in pursuit of the shiny new thing). I download a lot of tracks and podcasts, a variety of sources. No real problems to date.
My Venuezalan colleague says that if you are visiting Caracas then head to Sambil Mall (Largest in City). They apparently have a Nike store and various other sports stores covering Reebok, New Balance and Mizuno.