Where can I buy the 24 volt transformer that controls the thermastat for the carrier weathemaker 8000

All you need is the basic info off the old transformer, voltage and VA , you should be able to get one from any heating and air company or even a wholesale store.

Its just a 115 volt 30va transformer. Should be able to find it at any hvac supplier,electrical supplier and big box hardware store. Are you sure it's a bad transformer blown and not the low voltage fuse blown?

Yes, check the fuse. If the transformer is fried and it doesn't have a fuse, add an inline one. I once bought a fuse holder and transformer from Radio Shack.

There should be a factory installed 3 amp fuse just above where the 24 volt transformer wires connect to the printed circuit board.