That saw has a router/jig saw mount kit available. The holes in the table line up with holes in the mount plate (1/4" aluminum), and the mount plate is pre-drilled for Ryobi router base though most craftsman bases fit as well. Yours may line up.
The Router Mount Kit comes with a two piece fence that attaches to the saw's rip fence, dust shield, etc. Can usually be found on e-bay or Amazon for $50 to $80. Home Depot sells an 8 piece accessory kit (listed as "ryobi accessory kit" stock number is bt3kit) for $99 that includes the router kit, nice pair of casters, various throat plates, and a great clamp for the miter fence. Better value than just buying the router plate--at least i think so!!
You could build your own mount plate, it's a basic rectangle with two corners lopped off, use the underside of the BT3000 accessory table as a template. The kit above has served me well--i keep an old craftsman router attached to the plate and quick attach with the four above table screws when i need it. I'm finally getting ready to build a router table, so hopefully i can retire that part of my BT3000 soon.