If it works and you live in a craigslisty area, try doing a curb alert. More people are building MAME cabs than you think, and those 21" CRTs can be hard to come by at a decent price. I'd pick it up but it's kind of far.
I decided to restore my MAME rig back into an arcade game and now I have a large 21 inch computer tube monitor taking up valuable real estate on my garage floor. How do I get rid of it nowadays? I know Goodwill would not take it as is, and I can't just put it in the trash can.