Hi,

I don't know of a source for you, but I wanted to mention
that Heath used exactly that system (P7 phospher CRT with yellow filter)
in the SB-620 "ham-scan" spectrum analyzer (3RP7 CRT).
The earlier HO-13 ham-scan used a 3RP1, but also used a yellow filter.

73,
Ed Knobloch

Steven Swift wrote:
According to my DuMont handbook of CRTs, a yellow filter can be
used with a P7 phosphor CRT to allow viewing of the long decay
part without being "blinded" by the bright blue trace. I've searched
Ebay, Sphere Research and other sites looking for these.