I finished this little Ozark Boxcab from their kit last year, when there was nothing else to do. It is surplus to requirements, as I have 2 more similar locos!
It is self-contained with batteries and speed/direction control. It has cost me $125 for the kit, $80 for the sound, $20 for the electronics and a few $$ for other pieces like the couplers. How about $215 +shipping?
The motor block is from Hartland and has had little use. The body contains 3 Li 18650 batteries tucked in corners with a (new) protection board, and it comes with a charger. In the roof is a speed control with on/off and a black cover disguised as the diesel stack. The center of the rood has a vent which is actually the forward/reverse. The headlight comes on with power so you can see it is live. I added the radiator from a box of car bits (thanks, Bruce).
The coupler is a sprung Ozark link-and-pin. I usually insert a Bachmann coupler in the pocket (after chopping bits of it off.)
Here’s the thread on the construction. There’s a video on page 4 (last) of it in operation.
Let me know if you are interested.