I picked up a saw vice at an antique store or flea market years ago.
Saw sets are easy to find, most antiques stores/junk stores that have old tools have them.
$7-$10 should buy one. They have a setting that allows you to dial in the degree os set. Using a saw set it about the only way to get the set in the teeth the same.
Then a small tri-angle file and you are ready to go.
You can clamp the saw between two boards in a regular vice if need be.
And if the saw you are working with has some set in the teeth, then the only thing you need is a file.
File each tooth as the same angle it was originally, if you can.
good luck, Gene