the toshiba player, at the least the one in the first link, claims 18 hour battery life due to "advanced lithium ion rechargeable battery." it recharges in 3 hours and 30 min. the condition of use listed for the 18 hour battery life is: room temperature (25 deg. celcius), no backlight, volume at mid-level, 128 kbps WMA audio file sampled at 44.1 kHz.
so i guess such batteries are out there...
regardless, mp3 players aren't as popular (yet) in japan as MD players still command quite a bit of respect in regards to the portable music player industry. also, due to the fact everyone japan has a cell phone that are far, far more advanced than anything in the u.s., i imagine a cell phone mp3 players will have a better chance of succeeding.
i only mention the thing about japan because usually, japanese like their gadgets small, useful and well-designed. japanese aren't as price conscious (i.e. cheap) so once japanese market demands improved choices in mp3 players, i imagine good stuff will come out of japanese companies. (another reason apple does relatively better in japan, i think...) until such time, ipod is plenty capable and designed well enough to satisfy the japanese...