I would like to add my two cents. Many latter day NTSC decoders besides wider chroma and luma bandwidth also employed comb filtering to better separate the chroma from the luma. Not to fully dissuade you, I think it is better to leave the set as is until a replacement can be found.
I have mused to myself what would it take to build a display tube replacement employing a flat panel display. Resistive loads could be included to properly load the power supplies. The RGB applied the tube could drive the flat panel display. The biggest problem would finding a flat panel to fit the cabinet aperture without modifying the set or the cabinet in any way. It would just be a slip in replacement. Certainly the volume normally occupied by the original CRT could easily accommodate the modern interface electronics required.
There is a fair bit of work involved (mechanical and electrical) but it at least would provide a means to display an image in absence of a 15GP22.
Please be as cynical as you like in your response.
