calibration

What's a good source for 'deionized water' to use in calibrating a PH meter?

Hey guys, I am totally confused. I understand my TDS meter is testing the electrical conductivity of my water, but I just dont get how it all relates. I know there is a diff on how meter is built, 500 or 700, and that this affects the actual reading I get back from my meter. I am if I got a...