PULSAR gen 1 and 2 parts HELP!!

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I've been lucky enough to get my hands on two military issue Pulsar watches V657-X063 and YM92-X170, although neither have the case back! which i knew when i purchased them.
Naively I thought it would be easier than it is to find them. So any help would be much appreciated. Civvy/military/ generic - I really don't mind, for me I just want to wear and enjoy them.

My questions are

I know there are civilian models of them - but not many as spares kicking about, so do any other Seiko, pulsar or lorus models share the same back? do you know specific model codes?

will any watch with the same movement share the same case back? for example i read this "Pulsar YM92 movement–identical to the Seiko 7T92" so would any 7T92 caseback fit?

Seiko service centre were no help, just saying they're discontinued. i said, what about the versions you still sell in argos?! do those parts fit.. they just said its discontinued and don't stock parts.

Does anyone have any parts kicking about themselves?

are there such things as 'generic' case backs? are there standard sizes?

THANK YOU ALL IN ADVANCE!