What fitting do I need to ground EMT at my residential electrical panel?
The standard metal coupling suffice, if you install them properly.

This one is a compression style coupling, but the setscrew style will suffice as well.
You make the ground contact by running that conduit nut down and bapping it tight with a screwdriver blade and hammer... and tightening the compression fitting or setscrew.  After 50 years in a quasi-outdoor building, I can attest that it works fine.