1994 Geo Prizm help please

1994 Geo Prizm

ok here is my question what is this part called and where abouts may I find it you know the harmonic balancer ok on my car it got stripped out by that little key on my lower timing gear that makes everything rotate where can I find that little key and what is the appropriate name for it oh and sorry money is a issue at the moment for a donation but whatever I can do to help in return will be done