Looking for a manual, battery, and possible charger for Sony still digital Mavica FD75

SOURCE: How to shut off disk protect

disk protect is activated by the position of your floppys plastic protect tap ..When the tab is on protect position it depresses or opens a small switch on inside of cameras floppy drive .Decide wether it opens or closes and tape down switch on floppy drive .If it need to be open simply remove tab on floppy disk

SOURCE: I have a great Mavica

You probably need a new Sony "Infolithium" battery, by now. The battery lasts a long time
but 10 yrs IS a long time! If you've never repl
aced the battery, it's time to. They charge ok
but don't last very long when they're near the
end of their life! (Sounds like what you're
describing.) The little disc battery only works
the memory for the Date / time / etc.

SOURCE: my sony mavica mvc-fd81 turns on for only seconds,and turns off.

Have you tried another battery?
Even the lithium ions will eventually not hold a re-charge.
If the unit stays on with external power, there is a good possibility that a new battery will solve the issue