Find a specific file with automator
Usually "broken alias" refers to an alias where the original file no longer exists. I have used this script to find aliases like that:

set l to {}
tell application "Finder"
    try
        alias files of entire contents of (POSIX file "/Users/username" as alias)
        result as list
    on error
        return
    end try
    repeat with f in result
        try
            original item of contents of f
        on error
            --move contents of f to trash
            set end of l to POSIX path of (f as text)
        end try
    end repeat
end tell
set text item delimiters to linefeed
l as text


If the script finds the aliases you want to replace symlinks, save the relevant lines of the output to a text file. Then try running a shell script like this:

cat /tmp/aliases.txt | while IFS= read -r f; do
  original=$(find ~/directory/with/original/files -name "${f##*/}" | head -n1)
  echo "$f:$original"
  # rm "$f"; ln -s "$original" "$f"
done