I got mine from a thrift store a few years ago and Nakdoc fixed it..
A hint: modern batteries are too big and can get stuck.
I have a yellow and black R5 as well I got from a fiend on eBay and it was a donor but made to run as well.
Keep looking hard, they aren't common and not necessarily working..
I would highly suggest joining this site
http://www.stereo2go.com/forums/