There is an SWG 5HD on ebay (290,000 btu)
This link is broken, either the page no longer exists or there is some other issue like a typo.
It's not stainless but for a starter setup it might get you going. SWG doesn't list coal as an approved fuel and yet the SWG 4HDs is supplied with both Alaska and Liesure Line stoves. Before you plan on using anything though you need to talk with your local Fire Marshal and Insurance agent to make sure you will not cause yourself some issues or even worse loss of your home later on!
The folks at Keystoker are very helpful, I would also give them a call and see what they say.