Traveller, Triguard will be adding a 40mm series of buildings for the AWI/FIW ranges this year. Based on the examples available from places like Fort Loudon in Tennessee, we will make urethane models that you will need to assemble yourself, and will give you some flexibility in the sort of forts you can build. These will include a block house.
I can't give you a delivery date yet, but the aim is sometime in the first half of this year. Apologies if that is not fast enough.
Phil