Welcome to the forum!
Is that a picture of your starter or a picture you found?
Anyway, there was discussion about that spring here
https://cj3apage.com/Forum/index.php?topic=3181.0No one mentions a source but there is a picture in post 15.
I looked at mine and it appears to be a spring I "re-purposed" from something else.
Some home improvement stores have a pretty good selection of springs, you may find one there. I checked Walck's 4wd but found nothing.
Randy