You mean the "AGA Go" kit by DCE. That was essentially an A1200, mounted on a CPU card that goes into an A500. More expensive than a new mainboard, therefore never mass-produced.
The only connection between A3000 and AGA is a prototype mainboard that Commodore made during the development of the AGA chips. Here's a photograph of one that I took when I visited Dale Luck in summer 2003. Note the hand-written serial number #28 ;-)