Just to add to the other post
It's very easy job to make your own mounting plate
Select you plate stock, like some 1/4" thick plastic,,cut it into a (9" x 12" or 11" x 11" ) draw a line from corner to corner, this will give you a center point , take it to the drill press and drill a 1/8" hole in the center and then drill it out to 1/4",,besure to clamp it to the table top.
Once you have the 1/4" in place,,fine some extra screws the same size as the mounting screws,,clip the heads off the screws and chuck them up in your battery power drill,, grind them all to a sharp point and then screw them in the router base with the sharp points sticking out,then chuck up the 1/4" drill you use to drill the center hole,, then put the router on top of the plate and with a hammer tap the router base ,this will give you a place to drill the mounting holes out, start with a 1/8" then drill it out to the right size hole and counter sink the holes..
Once you have that done chuck up a hole saw or a forester bit 2 1/4" hole size..,if you don't have a hole saw that size use the 1/4" drill bit to line it up on the drill press and then drill the 2 1/4" ,besure to clamp it in place b/4 you start..
Then you have a mounting plate that with fit your router ...
I've blown the dust off my Ryobi RE600 and want to mount it in my new router table but to make a new insert I need the original base to drill the mounting hole locations. The original base is missing and only God knows where that is and he's not talking. Does any one on the list have those mounting holes measured out? If so I'd sure appreciate a copy of those measurements so I can make some jigs and the table insert. Thanks in advance.