Ignoring the fact that the plug with screws will not fit in the console, will a standard 9-pin serial cable (this for example) (http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10212&cs_id=1021205&p_id=476&seq=1&format=1#largeimage) work as an extension cable for Mega Drive/Atari/etc controllers, or are the wires at different pins as different ends?
If you found a boring old M-F 9-pin serial cable, you'd probably be OK, but this one specifically says it's a null-modem cable. It's also known as a crossover cable, 'cause some signals are crossed over. It won't work for you.