At a flea market, maybe...these things are as obsolete as they come. You may enjoy the bit I wrote on the Glossary page about them, https://homerecording.com/glossary.html and I would suggest getting a nice shiny new CD player, unless you have a 1970s classic car and want to keep the audio technology in the same era.
You can also purchase an adapter to play cassettes in your 8 track machine. You just stick the cassette in the adapter and input it into the opening for the 8 track. That way you can keep you "classic" car original and listen to what you want.
Actually, Green Hornet (and welcome back BTW), it seems that Ask Jeeves is mostly geared towards providing hits for its e-commerce partners and not really answering your question (just try to find this site there and you'll see what I mean). If you really want to connect to multiple search engines, try http://dogpile.com
Punch in the following site and just ask where you can get those old, old, old, 8 track jumbo cassettes: www.askjeeves.com
This site will connect you with almost all of the search engines in seconds and, from there, you should find some one or some place to stock up on the 8 tracks.
I was hiking one day (Southern Ontario, try it sometime!) and dumped by a tree I found about 40 (!!!) 8-track cassettes.. I've been trying to find a cheap used player to find out what's on them. No labels, and either black or orange. I can send them to you if you want The rain hasn't hurt them... all.. that much... ummm.... maybe you'd better ignore this message
It's raining and I'm not on the golf course; thus, I popped into the office to check to see if my name was still on the door and to check my E's. Always like to drop into your site to learn and help. Since I teach for a living, my students are very keen on good info sites.