[i have 2 phase one batts and a canon bp911/15 its cheaper but lasts less, exactly the same per $/time. (the canon was 40% cheaper but lasted 40% less) just go for the phase bats, buy a few perhaps a dealer will give you a discount. i looked too for cheaper batts, but didnt want to risk it.
now if you can find a AC adapter for a back (for a camcorder) that will work, that would be cool!