The critical parameters are:
Here's a short list that may or may not contain the ideal replacement, then compare thermal and other specs
closest so far was an ST diode.
STTH1202 NO Good 200V
instead consider this 600V
The Sanken part is still the best (but even those can fail if caps also degrade)
30ns max. @ 0.5A 25°C 33ns max @ 1A 25°C
1.5V @ 10A 2.9V @ 12A typ **worse, may need bigger heatsink**
100uA @ 600V 25°C 20uA @ 600V 25°C (better)
20,000uA @ 600V 150°C 400uA @ 600V @ 125°C ( better but tested with lower heat stress)
4°C/W to case 2.4 °C/W to case ( better )
also search "ultrafast 600V diode Sanken stock"
All these specs above are tradeoffs so Sanken in Japan were pushing the envelope.
My suggested replacement may still run hot and fail early unless heat rise is checked after unplugging. If burning hot to touch, a bigger heat sink may be needed. A DMM can check if voltage has decayed to a safe level before touching. Don't if unsure.