Old outdoor spigot repair parts

Hopefully someone can help.
Attached pictures of an exterior spigot which was leaking 'all over'
As you can see the screw which held the valve seat washer is rusted out
Questions: Where to find replacement parts? Ideally would like to purchase an entire new stem.

Body of spigot is embedded in cement wall, so we don't know if it is soldered on or screwed in.
Would any indication allow us to tell if this is a screw in? If it is screw in, we would remove the existing spigot and replace with new.

Thank you

...........

Hello Frodo
Thank you for the reply.
As the post indicates, we need a bit more assistance than this.
How would one remove the rusted out screw? Where does one buy a new valve seat washer and screw for this relic?

take the valve stem with you to a plumbing supply house
NOT a hardware store
do not enter the door that says showroom, but enter the door that says counter sales
you should encounter a couple of guys hanging around a coffee pot.
be careful, they are plumbers, a dangerous breed of carnivorous animal
look them in the eye, and give a curt head nod, proceed to the counter
at this point, the coffee pot plumbers are watching you.
ask the guy behind the counter if he has any bib washers.
if he says yes, THEN, produce the stem, and ask how do you remove this screw.
OH OH..you just aroused the interest of the coffee pot plumber
He my or may not ask to see the valve stem, It all depends on if he is hungry or not
ask his opinion if the valve stem is repairable or trash
you may have to buy a whole hose bib, remove the stem to use on your faucet
take a picture of the old faucet, take the picture with you to the supply house
incase you are asked what kind of faucet is it