Things to look for when hunting TV sets for tube swaps:
Make sure the set is ACTUALLY a 19" set. Measure if you have to. Many are 20".
Avoid Sony Trinitron. They're a different type of tube and won't work in an arcade chassis. They are, however, fantastic televisions and will give a very nice picture.
Look in the vents in the back with a flashlight and look at the tube neck - the "narrow" tubes are good for 19" K7000's, and the "wide" tubes are good for most other monitors. Sometimes you can even see the tube number through the vents, you can look that up in the tube tester manual to see what kind of neck pinout it uses. CR23 (wide neck) and CR31 (narrow neck) are the ones to look for.
It's mostly a gamble, really. Some people try to make lists of what TV's make good tube swaps... but it's never going to be a complete anything. There are THOUSANDS of different models of television sets. Not only that, but it was pretty common for the internal parts to change even within the same model - casing is the same but the electronics are slightly different. Many cheap Chinese sets even had neckboards printed for either narrow or wide neck tubes, and simply had whatever socket they needed soldered on, allowing them to use whatever tube was cheap that week.
So, do some looking and take your chances, I've had very good luck. Also, if you talk to the guys at the store, you might be able to get broken sets for free - you don't care if they work, since you just want the tube. The tube is the only real re-usable part (occasionally the yoke), but the rest of the set is pretty useless, although I've been known to scavenge parts such as the degaussing coil, filter caps, large resistors, degauss thermistors and other components.
-Ian