I don't know how common coal stokers are in AK but I would watch craigslist, local ads etc. and look for a used stoker.
Here in Utah I saw about half a dozen stokers (residential size and a couple big ones) come up for sale this summer and one was free and in good shape... it was still in someones house, not rusting away out in a barn somewhere. Most advertise for $500.00 or less. There's an old Lennox stoker for sale now for $500 but I don't know the condition.
Sub-bit would be fine for one of these stokers.
These stokers have fans to circulate heated air and can be used as a space heater or connected to ductwork in a home. They can run a few days without tending (in most cases).
What size is this chestnut coal? Soft coal stokers use stoker coal about 1¼ to ¾ inches in size.
Never heard of someone building their own stoker before and I think I would be afraid to leave the house with a homemade stoker running
If you're patient I'll bet you could find a used stoker.