Best price I've seen has been for about $70 @ Wally-World (Wal-mart) - but it's pretty much a standard kinda thing. Other ones I've seen have had things like mutliple access codes and courtesy lights, and run anywhere up to $140.
I'm not so sure about buying something like this online unless you're sure you're getting a good deal, merely for the cost of shipping vs. getting one locally. Best place to look would probably be the auction sites (gunbroker.com, auctionarms.com, etc. Even eBay has these every now and then.)
Personally, I bought a non-keypad one. I can see myself forgetting the change the battery, and then when I need quick access, I'm screwed. Better to be used to using a key, IMHO.
As always, merely my 2 cents...
*** edited for my bad grammer ***