How easy will it be for people to get hold of replacement batteries for the HD5 in the future? I can't find it on amazon now (but it could be well-hidden). Does anyone know whether it is a bespoke HD5 battery, or whether it is common to other things, such as mini-disk players or other such technology? Its all well and good having replaceable batteries, but what happens if Sony don't continue to make them available because they are moving away from the HD5? Cheers!