I got lucky and picked this up off eBay for $200 with "Buy it now". It was a 3.5 hour round trip to pick up, but it was worth it. It had no marquee and didn't boot past the rug test. I happened to have an extra Defender marquee already. The CPU board had battery acid damage from old AA's that leaked. I removed the old battery holder and replaced it with a coin-type battery holder and battery. I replaced three ROMs that had broken pins (the old style ROMs with gold pins), all the RAM, 12 RAM sockets and a bad 74153. That got the game to boot, but there's a 1/2 inch strip of garbage on the right side of the screen that I still need to fix. The monitor needed a cap kit, the control panel was pretty worn around the joystick, the monitor plexi was carved up a bit, and the speaker grill had been punched through and covered with a "Realistic" speaker cover from Radio Shack. At least the cabinet art was in real nice shape.
I got an entire new speaker board with intact grill from eBay for $10. I bought a repro control panel overlay, buttons and monitor bezel from The CPO is beautiful, but I was not happy with the repro bezel. It's very different from the original. It's some kind of Stargate/Defender hybrid and is a different height with different art and the area for the instruction card is too big to use the old card, so I had to make and print a custom-sized Defender instruction card. It took far too much work to make the bezel fit and look right on the machine. Oh well. Now that it's installed, if you don't compare it to an original, it looks fine.