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Just get the BP-E1 which allows you to use both AAs and the CR25 housed in the grip. It adds very little bulk to the camera and if you use rechargeable batteries, frankly the weight isn't much to consider.
I really appreciated my BP-E1 in my college days when I didn't want to shell out $11.95 per 2CR5, and would use rechargeables instead. For me, it was a no-brainer, given that I didn't want to have the drive booster on my 1N all the time.
Try it, you'll like it.
Doesn't work with the 1V....