There's at least 3 different MP3 capable CD players on sale at Wal Mart. For quality MP3 CD players, check out iRiver.
http://www.iriveramerica.com/products/iMP-50.asp
As of MD, for under $100 you won't get anything that'll keep you happy. Even on eBay. If MD standard was a horse, someone would have shot it a long time ago.
I gave MD a fair chance. When I worked at a radio station, it was a de facto. All the junk was stored on MDs. I even had an MD in my car. Sadly, after years and years of this format on the market hardware prices are still higher than those I've seen in Japan 5 years ago. It's just a matter of time till it's gone.