Is it possible to get a magnetic mount to attach to my aluminum tablesaw base?
I'd suggest clamping a piece of steel in place temporarily -- or using a meter which references from one of the miter gauge slots -- or combining the two by getting a piece of steel made to fit comfortably in the miter gauge slot.

(I have a plastic fitting which lets me use a micrometer that way. I think I paid $10 for it at a woodworking supply shop.)