It seems they're available for little money on eBay and nothing says retro better than a genuine CRT. The display just has a different look to it, especially a monochrome tube. Monochrome tubes have no shadow mask to make red green and blue 'pixels'. It's just a uniform coating of phosphorescent material that the electron beam scans over uninterrupted and I always preferred this look. It's less tiring than a colour CRT display in much the same way the e-ink display of a Kindle is easier on the eyes than the standard screens in most tablets and laptops.
After about ten minutes of messing about, mostly taken up by finding suitable cables, I got a Raspberry Pi desktop displayed on it. No I don't really know what use this is yet but I love it.