The sound professionals have what you need specificly for Micro Track 1 for $49.00 and the other for $59.00 Say's adds 7+hrs for the one that is $49.00. 8+ hrs for the one for $59.00. So far I picked up the Micro Track mic they made and it is sweet. I'm waiting on the battery pack to come in the mail. I love my MT. Have used it many times for live recording. No complaints.
The same unit is available for less here:
http://www.newegg.com/product/product.asp?item=N82E16855998033
$34.99
ADVISORY: There is NO exact battery size stated, or just what type of regulater (efficiency?) is being used to maintain the 5 volt output from 3.7 volt lithium cell battery.
If battery size is 1000 ma, then run time with fully charged MT internal battery is less than 4 hours BEFORE needing to use up the internal battery of the MT deck. Because regulaters are NOT 100% efficient, likely less time, like maybe only 3 hours additional time, and only if MT battery is already fully charged before connecting the external battery device.
This gives total ~7 hours run time where 3 hours is the external attached battery, and maybe four hours is solely from MT internal battery if its in TOP condition.
If the MT battery is NOT fully charged, then the external battery may last only 2 hours before needing the internal MT battery to take over running the deck.
Somebody needs to actually run this external pack and post the recording time available.