Does anyone have a link to a source for 1/4" alignment/calibration tapes?

You might try US Recording Co (http://www.usrecordingmedia.com/).
They offer calibration tapes See Here (http://www.usrecordingmedia.com/noname2.html)
They also provide some good information so take a look at their HELP and FAQ sections.
Jim

. . .as I suspected, thanks.