Hi Scated,
Had the same situation earlier this year and replaced the OEM battery with one from AutoZone.
Since then no problems in 3K miles (Rocky Mountains (cold as hell) or Death Valley (hot as hell)).
However: the AutoZone battery comes with some specific directions to follow prior to initial use. Harlan (sort of a stepson, and a Bird owner himself) has worked at AutoZone for several years cautioned me that they had a high incidence of early failures in batteries not started up according to the directions.
Good luck,
Michael Pavlick