Set screw for power steering pump?

Pardon if this double-posts, it looks like my news provider is not
propagating.
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To keep a long story short, somehow the set screw for the power
steering
pump* on my 940 (B230F) backed itself out and ran off. I've since
locked a position by hand, but when I make sharp turns (i.e. parking
lot) my dash goes nuts, and I have an awful belt squeal at low
RPM... which, fun though it may be for pedestrians, does drive
me nuts when I roll down the window.

I'm blessed to live in a city with scads of hardware stores but
not many junkyards, at least for this vintage. Does anyone know what
the size of the screw is so I can pick up/special order one? Is it the
same
size as the screw for the alternator? For obvious reasons I'm most
concerned about length and shaft width.

Thanks in advance,
-TC

* Maybe not the power steering pump? It's below the alternator,
and links to the outermost belt on the shaft.