I got my NiMH replacement off Ebay... Dirt cheap... A few minutes with a soldering iron and a little amonia to neutralize/remove the battery acid. Works great, well worth the effort.
In my case, the new battery was 3 prong, but taking a vacuum desoldering tool to the 3rd hole on the motherboard fixed that.
Another thing on the A4k you have to watch is the SIMM sockets. The plastic on them decays over time and can break... Causing loose RAM modules. My fix for this when it occurs is a tiny amount of superglue, applied with a straight pin, to the sides of the SIMMs to hold them in place.
Just an extra tip :-D
