1974 5 speed Sprite SN NN4_____

Rebuilt it.
Took chain off the remove rust and limber it up.
Took pin out of link and accidentally pushed it all the way out.

Should I buy a pin, or a fix it link, or a new chain.

In all cases what should I get
and from where?

Uses original Huret Allvit read derailleur.

Do I need to use whatever I get specifically for 5 speed?
And or bike manufactured in Nottingham?


Thanks