For just a 1 time use, I have made them out of a bamboo skewer. Smooth down and fit snug through the hole. Cut to length with a jewelers saw. For a set I use often, I will turn out of steel, Bevel one end, And keep handy and secure in a pill bottle.
I have used toothpicks once or twice in the distant past. I would expect that you'd want something to fit a little more snug if you were shipping the trigger.
Also matchsticks work great. Cut to length with side cutter pliers. They slip in just right.
Put the sear safety cam/sear bar in the front hole first and slip a slave pin in. With a tweezers set the sear spring on its post. Turn the sear bar into its slot, hold down and insert the rear pin. Presto, takes about 30 seconds.