Is the salvage for the Mk12 ArmaTek Bayonet in the event store?

Yeah, the gear number of types vs available slots is such a bad ratio it can be annoying and close to improbable to refresh the store looking for the gear you need (or waiting for automatic refreshes).

I would suggest never spending the crystals on refreshing that store. Most likely you will not find the gear you need. Save your tokens; if you don't see the gear you need, spend on Yoda or Cassian U-Wing.