You're best off going down the eBay/second-hand route, where you'll be able to pick up a TV like that for next to nothing.
My local tip regularly has piles of old CRTs that people aren't able to (or can't be bothered to) sell.
Here's an example of a 25" 4:3 Panasonic Quintrix CRT that's currently going for £4.99 (not mine I promise - just using it as an example) :
Panasonic Quintrix 24" Television on eBay (end time 18-Oct-09 15:23:23 BST)
I had an identical set to this for 10 years and the picture quality was fantastic. I can't remember whether it meets all of your requirements, but I'm pretty sure it supported RGB/scart. The visible diagonal is around 23.5" IIRC.