The engram is:
"EngramEntry_Costume_Amongus_C"

The spawn command is:
cheat gfi costume_amongus 1 0 false

IDK what the blueprint path is. GL figuring it out.

I wanted to change the level requirement to 106 and make it cost 20 engram points. This means a player has to have beaten the overseer on at least easy difficulty and increased their level cap to craft this.

Here's how I did it:
In the game.ini:

[/script/shootergame.shootergamemode]
OverrideNamedEngramEntries=(EngramClassName="EngramEntry_Costume_Amongus_C",EngramHidden=False,EngramPointsCost=20,EngramLevelRequirement=106,RemoveEngramPreReq=false)