Where can I get a Jag-Stang whammy bar?
If you need to get a replacement tremelo arm for your jag-stang keep in mind that the jag-stang bridge is the same as a Fender mustang bridge.
So you can also look for a Fender Mustang Whammy Bar or Tremelo arm.
Note that there is a small allen screw that holds the tremelo arm in place. So if you’re missing that screw you will have issues keeping the tremelo arm set as you like.
Allparts carries a mustang tremelo arm for example. [allparts link]