Only a dealer will be able to get you an ignition key. Take the vehicles VIN number with you and proof of ownership, unless you're having the vehicle towed in.
Apparently not all of the 2000 4Runners had the chipped key. If you did and still had a working key, you can have a new key cut at the hardware store and program it your self. Blank transponder keys are about $10.
I think you're stuck going to the dealer if you lost the only key. They can pull up the keycodes from the VIN and cut a new key. I'd call the local locksmith and ask if they can do it though, as they'll be much cheaper if they can.
About 5 years back on a weekend at the Mall, the wife lost her keys to her 2003 Focus. We called AAA and they sent out a locksmith. The Key was chipped and he had all the tools to make one on the spot and program it. Actually had him make 2, as she only had the one set.
A locksmith can do it. Thats what they do. It might be cheaper at the dealer tho. I would call and ask which is cheaper. Some manufactures have cutoff years where they stop supporting keys and if thats the case you will be left using a locksmith.