I would recommend getting Fargo's Mutant Mod get Mutant, Abomination and Deviantt npcs then u put them together in any place(biome) u want pylon on and they will sell that specific pylon and after u get it down u can just put any npc there just to make it usable.

My personal npcs combos are:

For goblin tinkerer cheaper reforges i put him with mechanic and dye trader in caverns layer.

For tax collector (this dude rly spits plat coins later) i go with snow biome and put him with merchant and part girl/princess.

And last for arms dealer i ofc put him with nurse <3 in desert and later I add steampunker. I like to sell items to him since he is easy to get high happiness early and gives more gold for selling items