I actually answered him. But for other people seeing this.

First, you cannot obtain another weapon in this gamemode. There is only one weapon, and the owner is called "Dedective". Only Baiter/s can obtain a "Fake Knife" by collecting 5 green items.

For your question:

I'm not the one putting green items to the maps. Mappers are putting them.

Usually maps starting name with "mu_", "md_" , "murder_" have green items. But for our gamemode we recommend you play maps with rooms.
Like:

md_clue
md_tudor_hall