You got yourself a real gem of a power amplifier there. That Kenwood M2A is real nice and can provide some power for your speakers.
Just about any basic two prong female to male power cord should do. You can find them on Ebay, electronic store's, etc.
Here's a couple of place's that sell them:
The Roland keyboard use seems to be the most widely supported, and I found a musicians supply store that ships next day, so it will arrive around the time of the M2A.