If you look at
you will find the spec of most of the Russian tunnel diodes you are likely to find. You need Germanium, not Gallium Arsenide, 'switching', and a peak current Ip that matches the spec of the original part. I think Ip was 4.7mA for the 454 diodes, the 453 may well be different. The Russian parts do not have a tight spec for the capacitance, low capacitance gives a faster switching speed, I doubt that the switching speed is critical for the 50MHz 453. When I was looking at the Russian tunnel diodes some years ago it was much easier to find the stripline packages rather than the wire ends.
Roger
