Up for sale here is this set of two metal bottom covers from an Onkyo A-7 amplifier. These are in good condition with light to moderate wear, but one piece is a bit bent. It still fits on the amplifier (not included) just fine, and you could flatten it pretty easily. No hardware is included. These might fit the A-5 and A-10, but I don't know for sure. Please see my pictures for details and measurements.
US shipping and handling is $20, and international is $75. If you have any questions, please ask.
I have more Onkyo parts and other vintage electronics listed--feel free to take a look!