Where's the best place to buy an earthquake preparedness kit?

Rome. ;-)

I would suggest making your own. That’s what we did.. We basically sat down and planned on what we would need for 7 days without assistance.

So:
-First aid kit
-2 gallons of water per person per day
-Food (whatever floats your boat)
-AM/FM radio
-Lots of flashlights
-Lots of batteries
-A tent
-A camp stove
-Cans of Propane for the stove
-Plus we put in some items to comfort the kids.. Favorite foods, candy, books, teddy bears
-Plus we put in some items to comfort the adults.. Vodka, beer, smokes

I would just think about how to address your needs and go from there. Buying a kit seems like overkill.

I did a combo of the above/buying a kit. I used a site called the readystore (just google it for the link) and it let me build my kit. They don’t make you buy a bag (unless you want to), you just click what you want and they send it in the mail.

www.beprepared.com

I live in AK and recently went through a 7 point something quake. Yes, it was scary as all get out. JrpowYesell’s post covers this nicely, tho’ I’d add few things. One, if you live in earthquake country, avoid putting large items/pictures/whatever above your bed. I was lucky, nothing much on walls, but others weren’t so lucky and felt like the world was falling in on them. Second, keep a flashlight handy and secured to something you think will remain stable. Earthquakes aren’t always nice enough to take place when it’s daylight outside (ours wasn’t) and a flashlight will be very important. A pair of shoes you can easily slip into, too, tho’ be sure to shake them out nicely just in case something has broken and left glass inside them.

As to your original question, I’d add to invest in at least a small generator. If it isn’t something you anticipate needing to use frequently, something that will power your lights and heat would suffice. Remember, even your smart phones need to be powered up occasionally! My iPhone was like my precious connection to the outside world at the time, so you might make a point of keeping that handy, too, in a secure place on your or nearby.

Oh, and to add to jrpowell’s list, don’t forget pets! Like children (and, yes, scared adults) they’ll need comforting, too, and comfort foods and toys.