These work in Overworld aswell!
What you want to do is have two coordinates!
I'll be refering to your coordinates as A and B.
The A coordinates are where you want the portal block, B as the destination. Example: xB are the x coordinates of B.
/setblock A end_gateway{ExitPortal:{X=xB,Y=yB,Z=zB}}
It's pretty useful, and im pretty sure it doesnt even do the big laser beam end gateways do.