Hi
I've just posted a tutorial for programming a new OEM remote for a 99 Camry.
A couple of things to consider...
Some of the non-OEM transmitters on Amazon or ebay are learning transmitters and need a working transmitter to learn from. These remotes should come with instructions for learning the frequency of the working remote.
The OEM transmitter has a set frequency which the car's onboard computer must programme and store. Refer to the tutorial for how to do that.
Also you can buy CR2032 batteries with terminals from Jaycar. Modifying and soldering is necessary.
Hope that helps.