I just finished a project a few days ago using one I had in my basement for years. I didn't think I was ever going to use it until one of my wifes friends started talking about how she loves them. I took her computer to fix it up (5 search bars in every web browser type) and a few days later...
To finish the project, I searched on craigslist. I found someone selling megatouchs (for a decent price) refurbished. I emailed if he had an empty case and he did. Trouble is, these things are HEAVY. So you should look local. But there are people who buy these in bulk, fix them up and sell them. Find one, and you will probably be able to drive and pick one up.
Also posting your real location helps here. ESPECIALLY when asking for CRTs.
btw, do you have control over the lighting? And want an interesting project? Consider building a multi touch. You rip a cheap lcd apart, and buy an old eyetoy camera... Put in some plexi and some infrared leds and you have yourself a multi touch system. Project usually takes a few days to a week depending on how much your willing to buy, compared to rip apart yourself. It also wont work in rooms with lots of natural lighting and some types of lights. But if the project is to get the kids to finish a project,
http://nuigroup.com/go/lite. I've built 2 so far...Fun as a project (but never did much with them after, one was in the shape of a cross between an arcade and a drafting table, and one was/is (not finished yet) in an arcade cocktail table. The cocktail table uses IR lasers, the old one used FTIR (leds being shot into a thick plexi and a projector.