kx250rider...Cool, that is indeed a flat phosphor screen! I must watch for a 210, since it appears to be the first, it would seem to be the most collectible. There is one on eBay right now, but it has a missing (or broken) volume control knob. Wiki says 1982 for this model... did you perhaps buy your first one in Japan earlier?
Even with the Zenith and Magnavox models added in, I suspect that a collection of ALL the the models of Flat CRT TVs could fit into a shoe box
Some of the "monitor" versions have appeared on eBay*, but the BIN price is above the 10 bucks (or so) that I like to pay.
http://cgi.ebay.com/SONY-WatchCam-Ey...item1c0d11d344
* not affiliated, etc.
jr