I found one on e-bay:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2533&item=5911927733&rd=1&ssPageName=WDVW
That one doesn't look anything like the "8 ball" I had back in the late 50s/ early 60s. It was black, 7-8" diameter, had white "8" on it, and a flat clear spot where an 8-10 sided "answer" appeared after I shook it.
I saw one recently driving by a yard sale. I was tempted to stop and get it, but didn't.