The Church of Alvis

Anyone have any advice? I have to replace my power cord brick thingy as mine is dead, and I was able to get the HP brand replacement part for a reasonable price, so I went ahead and picked that up. But my battery has also been completely dead for over a year, so I thought I might pick up one of those too too if I could find a cost effective one. But as it turns out the HP brand ones are like a majillion bajillion dollars. Is a compatible offbrand a horrid idea?

That depends on where you buy it. I would never get a new laptop battery off of eBay or amazon. 9 times out of 10 those are from the factory in China that makes them for HP. On the outside, that sounds good, until you realize those are the ones that the factory rejected. A few years ago there were several cases of laptop batteries catching on fire. A factory reject is too risky.
I'd stick to the official brand, or one from a reputable online dealer like newegg.