Replacement battery, what to get and where?

Archived from groups: comp.sys.laptops (More info?)

Well my Compaq Presario 1800T batteries must have lived their life. After
nearly 3 years, or is it 4 all ready, the batteries are lasting 5 min on
one, and an hour on the other. So it's time to find a replacement. The
question is while looking around I'm getting confused a little. The one's I
have now say Li-ION, and have powered the notebook from 2.5-4 hours in their
prime, enough to watch a DVD on a plane ride and still have about 30 min of
power left. I see some replacements are Ni-MH or Li-ION, which is better?
Also where is a good place to get a low cost replacement? I've been looking
over e-bay, only looking for "new" since any used could be what I all ready
have. But it seems hard to find an exact replacement for mine, since I have
a T in the model number. There are lots of 1800 batteries, but the part
numbers don't match mine. In the little bit of Googling I've done a store
replacement is about $130-$150. I like the e-bay price of $50-60 a lot
better. Suggestions on where I might be able to find a new battery for this
price?

Thanks
Bryan