The Yale key blanks are no longer available, too old, at least that I can find. ILCO doesn’t offer these blanks either. I have come up with an alternative blank that will fit the HGxx, KFxx & 4Xxx keyed Yale locks. I’ve made 2 different keys using this blank, they work fine.
You’d have to take this blank, along with its description, to a locksmith that can cut keys using the impression method.
As for the Union chest lock, you’ll have to post a picture of its key number. Then I can help explain your options.
Good luck……Ted