For a steady supply of level 1 through 3 treasure maps you should work the Dark Guardian room in Doom. There is a 100% drop rate on tmaps there plus other good loot for farming.
Samp is an easy farming method for these guys because you're immune to the poison in the room when they pop. Undead Slayer, EoO, Honor and you can pretty much two-hit kill each then barely have enough time to loot them (if by hand) before the door locks and they pop again.
Also, the more chars you have down there the more that will spawn so secondary accounts or a friend will increase your yield greatly!
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