Well, there's no fan driven smoke unit that's truly a "drop-in".
I use the MTH steam smoke unit with the short posts for TMCC or Legacy upgrades. I bend a chunk of 1/16" aluminum sheet for fabricate a mounting bracket, and then solder a brass tube extension on the screw-in funnel. I swap out the two 16 ohm resistors for a single 8 ohm resistor.