Need flyback diode for H-19

[Terry Fox]

One of my Heathkit H-19 terminals has died.  After a lot of troubleshooting, 
it appears that the diode in the high-voltage connection to the CRT has gone 
bad.  It is connected to the flyback transformer, then to the HV connection 
on the bottle.  I believe the flyback xfmr itself is fine.

Does anyone know where I can pick up a high-voltage diode that is suitable 
for old CRTs?  I've been googling and looking at ebay without any luck so 
far.  With everything gone to LCDs. it's difficult to find these parts.

Go CP/M!
73, Terry, N4TLF