[Arran]

 If you really can't stand watching a dim 7JP4 there are some scope tubes that will work as a cheap substitute, but the phosphors are P1 rather then P4, the drawback of course is that the phosphor is green rather then white. A lot of people go the scope tube route on one of those 3'' Pilot TVs since it's all too common to find one of the original 3KP4s with an open filament thanks to the goofy filament series string those sets used.
Regards
Arran