Most autoparts stores can order them.
Just make sure you order them by the part number, not by the car.
Every 3000 miles too much? ... I've changed plugs in Hyde at least 4 times in the last 2000 miles
This is the deal ... copper is the BEST connductor.
However, it wears fast.
If you have a mildly modded MR2 and want 10K miles out of your plugs ... go for the OEM platinums.
If you want the best spark you can ... go with the coppers.
At all costs, avoid the Bosch platinums! Worst plug for our cars ever.